Effectiveness of cold water immersion in the treatment of exertional heat stroke at the Falmouth Road Race

Exertional Heat Stroke Best Practices in U.S. Emergency Medical Services Guidelines

BACKGROUND

Exertional heat illnesses (EHIs), specifically exertional heat stroke (EHS), are a top cause of nonaccidental death among U.S. laborers. EHS management requires coordination between Emergency Medical Services (EMS) and workplace officials to implement cold water immersion (CWI) and cool first, transport second (CFTS).

OBJECTIVE

The purpose of this article was to quantify and identify existing statewide EMS guidelines, determine whether statewide EHS guidelines improved outcomes for EHIs in laborers, and examine the odds of laborer EHS fatalities when best practices are present in EMS statewide guidelines.

METHODS

The Paramedic Protocol Provider database and official EMS websites were examined to determine which U.S. states had statewide EMS guidelines and, for those with statewide guidelines, a two-way χ2 analysis with associated odds ratios examined EHI outcomes. Statewide EMS guidelines underwent content analysis by three independent reviewers regarding EHS best practices. Significance was set a priori at p < 0.05.

RESULTS

Among 50 states, the District of Columbia, and Puerto Rico, 57.7% (n = 30) had statewide EMS guidelines and 42.3% (n = 22) did not. There was a significant association for EHI outcome for states recommending CWI as a cooling method vs. those that did not (χ21 = 3.336; p = 0.049). The odds of EHS deaths for laborers were 3.0 times higher if CWI was not included in the EMS guidelines. There was a significant association in EHI outcomes for states without CFTS (χ21 = 5.051; p = 0.017). The odds of laborers dying from EHS were 3.7 times higher in states without CFTS.

CONCLUSIONS

Laborers are 3.0 and 3.7 times less likely to die from EHS when statewide EMS guidelines include CWI and CFTS, respectively.

Hyperthermia and Exertional Heatstroke During Running, Cycling, Open Water Swimming, and Triathlon Events

Few previous epidemiological studies, sports medicine position statements, and expert panel consensus reports have evaluated the similarities and differences of hyperthermia and exertional heatstroke (EHS) during endurance running, cycling, open water swimming, and triathlon competitions. Accordingly, we conducted manual online searches of the PubMed and Google Scholar databases using pre-defined inclusion criteria. The initial manual screenings of 1192 article titles and abstracts, and subsequent reviews of full-length pdf versions identified 80 articles that were acceptable for inclusion. These articles indicated that event medical teams recognized hyperthermia and EHS in the majority of running and triathlon field studies (range, 58.8 to 85.7%), whereas few reports of hyperthermia and EHS appeared in cycling and open water swimming field studies (range, 0 to 20%). Sports medicine position statements and consensus reports also exhibited these event-specific differences. Thus, we proposed mechanisms that involved physiological effector responses (sweating, increased skin blood flow) and biophysical heat transfer to the environment (evaporation, convection, radiation, and conduction). We anticipate that the above information will help race directors to distribute pre-race safety advice to athletes and will assist medical directors to better allocate medical resources (eg, staff number and skill sets, medical equipment) and optimize the management of hyperthermia and 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.

Outcomes of UK military personnel treated with ice cold water immersion for exertional heat stroke

INTRODUCTION

Despite mitigation efforts, exertional heat stroke (EHS) is known to occur in military personnel during training and operations. It has significant potential to cause preventable morbidity and mortality. International consensus from sports medicine organisations supports treating EHS with early rapid cooling by immersing the casualty in cold water. However, evidence remains sparse and the practice is not yet widespread in the UK.

METHODS

Following changes to enable on-site ice cold water immersion (ICWI) at the Royal Marines Commando Training Centre, Lympstone, UK, we prospectively gathered data on 35 patients treated with ICWI over a 3-year period. These data included the incidence of adverse events (e.g. death, cardiac arrest or critical care admission) as the primary outcome. Basic anthropometric data, cooling rates achieved and biochemical and haematological test results on days 0-5 were also gathered and analysed.

RESULTS

Despite being a cohort of patients in whom we might expect significant morbidity and mortality based on the severity of EHS at presentation, none experienced a serious adverse event. In this cohort with rapid initiation of effective cooling, biochemical derangement appeared less severe than that reported in previous studies. Higher body mass index (BMI) was associated with a lower cooling rate across a range of values previously reported as potentially of clinical significance.

CONCLUSIONS

This case series supports recent updates to UK military guidance that ICWI should be more widely adopted for the treatment of EHS. Clinicians should be aware of likely patterns of blood test abnormalities in the days following EHS. Further work should seek to establish the impact of lower rates of cooling and develop strategies to optimise cooling in patients with higher BMI.

Every Picture Tells A Story: Managing Exertional Heatstroke with Rotating Ice Water Towels

ABSTRACT

A 23-year-old woman completing her first marathon collapsed near the finish line at 4 hours 6 min with a rectal temperature of 41.8°C. She was in good health before the race with no recent illness, had completed a full training program, and was taking no medications or supplements. On the initial exam, she was unconscious with a response to painful stimulus, spontaneous breathing, rapid pulse, eyes closed, fully dilated pupils, poor muscle tone, and pale skin that was warm to touch. The medical team initiated whole-body cooling using rapidly rotating ice water towels and ice packs placed in the neck, axilla, and groin. She developed echolalia during active cooling. About 20 minutes into the cooling procedure, she "woke up," was able to answer questions coherently, and her pupils were normal size and reactive. She was discharged home with instructions to follow-up in 2 d for evaluation and blood chemistry testing.

Post-exercise management of exertional hyperthermia in dogs participating in dog sport (canicross) events in the UK

Exercise is a common trigger of heat-related illness (HRI) events in dogs, accounting for 74% of canine HRI cases treated under primary veterinary care in the United Kingdom. However, few empirical studies have evaluated the effectiveness of differing cooling methods for dogs with exertional hyperthermia or HRI. This study aimed to prospectively evaluate effects of ambient conditions and post-exercise management practices (cooling methods and vehicular confinement) on the post-exercise temperature change of dogs participating in UK canicross events. Canine temperature was recorded at three intervals post-exercise: as close as possible to 0- (immediately post-exercise), 5-, and 15-min post-exercise. Ambient conditions and post-exercise management were recorded for 115 cooling profiles from 52 dogs. In 28/115 (24.4%) profiles, the dog's temperature increased during the first 5-min post-exercise. Overall, 68/115 (59.1%) profiles included passive cooling (stood or walked outside), 35 (30.4%) active cooling (cold-water immersion or application of a cooling coat), and 12 (10.4%) involved no cooling and were immediately housed in vehicles. No dogs developed hypothermia during the study and no adverse effects were observed from any cooling method. In hyperthermic dogs, overall post-exercise body temperature change was significantly negatively associated (i.e. the dogs cooled more) with 0-min post-exercise body temperature (β = -0.93, p < 0.001), and not being housed in a vehicle (β = -0.43, p = 0.013). This study provides evidence cold-water immersion (in water at 0.1-15.0 °C) can be used to effectively and safely cool dogs with exertional hyperthermia. Progressive temperature increases in many dogs - even after exercise has terminated - supports the message to "cool first, transport second" when managing dogs with HRI. When transporting dogs post-exercise or with HRI even after active cooling, care should be taken to cool the vehicle before entry and promote air movement around the dog during transport to facilitate ongoing cooling and prevent worsening of hyperthermia during travel.

Body Bag Cooling with Two Different Water Temperatures for the Treatment of Hyperthermia

INTRODUCTION: Exertional heatstroke (EHS) is a life-threatening condition that requires quick recognition and cooling for survival. Experts recommend using cooling modalities that reduce rectal temperature (TREC) faster than 0.16°C/min though rates above 0.08°C/min are considered "acceptable." Hyperthermic individuals treated in body bags filled with ice water (∼3°C) have excellent cooling rates (0.28 ± 0.09°C/min). However, clinicians may not have access to large amounts of ice or ice water when treating EHS victims. The purpose of this study was to determine if using a body bag filled with water near the upper limits of expert recommendations for EHS treatment would produce acceptable (>0.08°C/min) or "ideal (>0.16°C/min)" TREC cooling rates or different nadir values.METHODS: A total of 12 individuals (9 men, 3 women; age: 21 ± 2 yr; mass: 74.6 ± 10.2 kg; height: 179.5 ± 9.6 cm) exercised in the heat until TREC was 39.5°C. They lay supine while 211.4 ± 19.5 L of 10°C (Ten) or 15°C (Fifteen) water was poured into a body bag. Subjects cooled until TREC was 38°C. They exited the body bag and rested in the heat for 10 min.RESULTS: Subjects exercised in similar conditions and for similar durations (Ten = 46.3 ± 8.6 min, Fifteen = 46.2 ± 7.8 min). TREC cooling rates were faster in Ten than Fifteen (Ten = 0.18 ± 0.07°C/min, Fifteen = 0.14 ± 0.09°C/min). TREC nadir was slightly higher in Fifteen (37.3 ± 0.2°C) than Ten (37.1 ± 0.3°C).DISCUSSION: Body bag cooling rates met expert definitions of acceptable (Fifteen) and ideal (Ten) for EHS treatment. This information is valuable for clinicians who do not have access to or the resources for ice water cooling to treat EHS.Miller KC, Amaria NY. Body bag cooling with two different water temperatures for the treatment of hyperthermia. Aerosp Med Hum Perform. 2024; 95(4):194-199.

Association between the experience of exertional heat illness (EHI) and living conditions of collegiate student athletes

Exertional heatstroke (EHS), a severe form of exertional heat illness (EHI), is the third leading cause of death in athletes; thus, early detection and prevention of EHI can help prevent EHS, which is a life-threatening condition. This study aimed to clarify the association between the cognizance of experiencing EHI and living conditions and specific EHI symptoms among collegiate athletes. This study was conducted in October 2022 by administering a questionnaire to 237 male collegiate athletes. Of the 215 (90.7%) respondents, 197 (91.6%) provided valid responses; among them, 88 (44.7%) responded they had experienced EHI, while 109 (55.3%) had not. A history of medical examinations due to EHI, having experienced headaches during summer activities, and having read the EHI manual were factors indicating cognizance of EHI. The number of times meals containing a staple food, main dish, and side dish were eaten in a day was a factor in preventing EHI. Early detection of EHI is important for its prevention, and it is important that athletes themselves have knowledge of symptoms and can correctly self-diagnose EHI. Emphasizing the potential of a well-balanced dietary intake has the potential to prevent EHI is crucial.

Exertional Heat Stroke Survival at the Falmouth Road Race: 180 New Cases With Expanded Analysis

CONTEXT

A high number of exertional heat stroke (EHS) cases occur during the Falmouth Road Race.

OBJECTIVES

To extend previous analyses of EHS cases during the Falmouth Road Race by assessing or describing (1) EHS and heat exhaustion (HE) incidence rates, (2) EHS outcomes as they relate to survival, (3) the effect of the environment on these outcomes, and (4) how this influences medical provider planning and preparedness.

DESIGN

Descriptive epidemiologic study.

SETTING

Falmouth Road Race.

PATIENTS OR OTHER PARTICIPANTS

Patients with EHS or HE admitted to the medical tent.

MAIN OUTCOME MEASURE(S)

We obtained 8 years (2012 to 2019) of Falmouth Road Race anonymous EHS and HE medical records. Meteorologic data were collected and analyzed to evaluate the effect of environmental conditions on the heat illness incidence (exertional heat illness [EHI] = EHS + HE). The EHS treatment and outcomes (ie, cooling time, survival, and discharge outcome), number of HE patients, and wet bulb globe temperature (WBGT) for each race were analyzed.

RESULTS

A total of 180 EHS and 239 HE cases were identified. Overall incidence rates per 1000 participants were 2.07 for EHS and 2.76 for HE. The EHI incidence rate was 4.83 per 1000 participants. Of the 180 EHS cases, 100% survived, and 20% were transported to the emergency department. The WBGT was strongly correlated with the incidence of both EHS (r2 = 0.904, P = .026) and EHI (r2 = 0.912, P = .023).

CONCLUSIONS

This is the second-largest civilian database of EHS cases reported. When combined with the previous dataset of EHS survivors from this race, it amounts to 454 EHS cases resulting in 100% survival. The WBGT remained a strong predictor of EHS and EHI cases. These findings support 100% survival from EHS when patients over a wide range of ages and sexes are treated with cold-water immersion.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2024 Update

The Wilderness Medical Society (WMS) convened an expert panel in 2011 to develop a set of evidence-based guidelines for the recognition, prevention, and treatment of heat illness. The current panel retained 5 original members and welcomed 2 new members, all of whom collaborated remotely to provide an updated review of the classifications, pathophysiology, evidence-based guidelines for planning and preventive measures, and recommendations for field- and hospital-based therapeutic management of heat illness. These recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks or burdens for each modality. This is an updated version of the WMS clinical practice guidelines for the prevention and treatment of heat illness published in Wilderness & Environmental Medicine. 2019;30(4):S33-S46.

Navigating implementation barriers: a holistic approach to improving exertional heat stroke management

Objectives

To assess the shift in medical volunteers' perception and practice surrounding exertional heat stroke (EHS) prehospital management after the Tokyo 2020 Olympic Games.

Methods

An online survey was sent to medical volunteers assigned to work at high EHS risk events during the Tokyo 2020 Olympic Games. Surveys were sent at the time of initial training, immediately after the Games, and one year after the Games. The survey investigated medical volunteers' perceptions and practices regarding the assessment of rectal temperature and the use of whole-body cold water immersion (CWI) as prehospital management of EHS. In addition, an open-ended question was prepared to examine barriers and facilitators of their chosen perception and/or behaviour.

Results

The lack of knowledge about rectal temperature assessment improved over time, but the actual implementation did not. Meanwhile, increased utilisation of CWI was observed 1 year after the Games. The lack of equipment, apprehension towards rectal temperature assessment, the perception of difficulty getting patient consent, concerns for hypothermic overshoot and the number of required medical providers were raised as barriers to implementation.

Conclusion

Some improvements were observed in perception and practice; however, further organisational and financial support is warranted for a broader skill transfer and implementation.

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

INTRODUCTION

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.

METHODS

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.

RESULTS

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 11-12 min when water temperature is ≤ 9 °C, and for 18-19 min when water temperature is 10-26 °C (Cohen's Kappa: 0.32-0.75, p < 0.001; diagnostic odds ratio: 8.63-103.27).

CONCLUSION

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.

Exertional Heat Illness: Adoption of Policies and Influencing Contextual Factors as Reported by Athletic Administrators

BACKGROUND

Little is known about the adoption by athletic administrators (AAs) of exertional heat illness (EHI) policies, and the corresponding facilitators and barriers of such policies within high school athletics. This study describes the adoption of comprehensive EHI policies by high school AAs and explores factors influencing EHI policy adoption.

HYPOTHESIS

We hypothesized that <50% of AAs would report adoption of an EHI policy, and that the most common facilitator would be access to an athletic trainer (AT), whereas the most common barrier would be financial limitations.

STUDY DESIGN

Cross-sectional.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 466 AAs (82.4% male; age, 48 ± 9 years) completed a validated online survey to assess EHI prevention and treatment policy adoption (11 components), as well as facilitators and barriers to policy implementation. Access to athletic training services was ascertained by matching the participants' zip codes with the Athletic Training Locations and Services Project. Policy adoption, facilitators, and barriers data are presented as summary statistics (proportions, interquartile range (IQR)). A Welch t test evaluated the association between access to athletic training services and EHI policy adoption.

RESULTS

Of the AAs surveyed, 77.9% (n = 363) reported adopting a written EHI policy. The median of EHI policy components adopted was 5 (IQR = 1,7), with only 5.6% (n = 26) of AAs reporting adoption of all policy components. AAs who had access to an AT (P = 0.04) were more likely to adopt a greater number of EHI-related policies, compared with those without access to an AT. An AT employed at the school was the most frequently reported facilitator (36.9%).

CONCLUSION

Most AAs reported having written EHI policy components, and access to an AT resulted in a more comprehensive policy.

CLINICAL RELEVANCE

Employment of an AT within high school athletics may serve as a vital component in facilitating the adoption of comprehensive EHI policies.

A case report of near-missed heat stroke

RATIONALE

Heat-related illnesses have protean manifestations that can mimic other life-threatening conditions. The diagnosis of heat stroke requires a high index of suspicion if the patient has been exposed to a high-temperature environment. Central nervous system dysfunction is a cardinal feature. Strict adherence to temperature criteria can potentially lead to misdiagnosis.

PATIENT CONCERNS

A 37-year-old construction worker was brought in by his wife and coworker due to a sudden loss of consciousness while resting after completing his work.

DIAGNOSES

Due to challenges faced during the coronavirus disease 2019 pandemic, as well as language barriers, a detailed history from the coworker who witnessed the patient's altered sensorium was not available. He was initially suspected of having encephalitis and brainstem stroke. However, subsequent investigations revealed multiorgan dysfunction with a normal brain computed tomography and cerebral computed tomography angiogram. In view of the multiple risk factors for heat stroke, pupillary constriction, and urine color suggestive of rhabdomyolysis, a diagnosis of heat stroke was made.

INTERVENTIONS

Despite delayed diagnosis, the patient's multiorgan dysfunction recovered within days with basic supportive care.

OUTCOMES

There were no noticeable complications on follow-up 14 months later.

LESSONS

Heat stroke can be easily confused with other neurological pathologies, particularly if no history can be obtained from the patient or informant. When approaching a comatose patient, we propose that serum creatinine kinase should be considered as an initial biochemical screening test.

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.

Whole-body cooling effectiveness of cold intravenous saline following exercise hyperthermia: a randomized trial

INTRODUCTION

In some athletic, occupational, military and emergency settings, cold intravenous (IV) fluids are used to facilitate whole-body cooling in an effort to treat heat illness. This treatment has anecdotal support, but currently lacks evidence supporting it as a whole-body cooling modality. Other modalities may offer superior cooling rates, and thus, patient outcomes following treatment. We sought to evaluate cooling rates of cold-IV normal saline immediately following exercise-induced hyperthermia.

METHODS

Eight healthy participants (3 females; 25 ± 2y; 72.9 ± 10.9 kg) completed 2 trials in random order. Prior to exercise, participants provided a small urine sample to confirm hydration status via urine specific gravity. Wet bulb globe temperature (WBGT) was assessed throughout trials. In both trials, participants exercised outdoors until rectal temperature (Tre) reached ∼38.9 °C, or volitional exhaustion, and then were cooled. In cooling, participants received either cold-IV (∼5 °C 0.9% NaCl fluids) or no treatment (sat in the shade; passive). Throughout exercise and treatment, Tre and heart rate (HR) were monitored. During exercise and every 10 min throughout cooling, participants were asked to assess thermal sensation.

RESULTS

Hydration status (P = .847) was not significantly different prior to exercise between trials. WBGT throughout was not different between trials (P = .426). Maximum Tre reached was not different between cold-IV (38.88 ± 0.30 °C) and passive cooling (38.76 ± 0.28 °C) trials (P = .184). Mean cooling rate for cold-IV (0.039 ± 0.005 °C·min-1) was significantly greater than for passive cooling (0.028 ± 0.005 °C·min-1; P = .002). Tre throughout cooling was not different between trials (P = .707), but did decrease throughout (P = .008), regardless of trial. HR was decreased over time (P < .001), but cold-IV and passive cooling were not different throughout HR recovery (P = .141). Thermal sensation decreased throughout cooling (P < .001), but was not different between trials (p = .278).

CONCLUSION

Emergency medical personnel should adopt treatment protocols that employ documented effective treatments for exertional heat stroke. In isolation, our data casts significant doubt for the use of cold-IV saline infusion for whole-body cooling of hyperthermic individuals.

Cooling Methods Used to Manage Heat-Related Illness in Dogs Presented to Primary Care Veterinary Practices during 2016-2018 in the UK

The management of heat-related illness (HRI) in dogs has received limited attention in the veterinary literature, especially regarding effective cooling methods. Guidelines published in 2016 for prehospital management of dogs with HRI advised "cool first, transport second", and recommended using cold-water immersion and evaporative cooling (water application with air movement) as the optimal approaches to reduce the patient's temperature. The current retrospective cross-sectional observation study analysed electronic patient records from the VetCompass programme to describe the cooling methods used in dogs with HRI presented to primary care veterinary practices during 2016-2018. Of 623 HRI events identified, 341 (54.74%, 95% CI 50.81-58.60%) included information on cooling in their clinical record. Of these, 74/341 (21.70%, 95% CI 17.65-26.38%) were cooled prior to transport for veterinary care. Overall, 23.97% (95% CI 19.24-29.44%) were cooled using one of the two recommended cooling methods, whilst the most common cooling method recorded was the application of wet towels (51.31%, 95% CI 45.34-57.24%). Canine cooling guidance and messaging in both the public and veterinary sectors requires urgent review to ensure that the most effective cooling methods are promoted because delays to canine temperature reduction worsen patient outcomes.

[Expert consensus on the prevention and treatment of heatstroke in children (2023)]

Due to the immature development of temperature regulation in the central nervous system, children have a weakened ability to regulate heat and are susceptible to heatstroke, which can lead to organ damage. Based on the evidence evaluation criteria of the Oxford Centre for Evidence-Based Medicine, this expert consensus group evaluated the current evidence on heatstroke in children, and formed this consensus through thorough discussion with the aim of providing reference for the prevention and treatment of heatstroke in children. This consensus includes classifications, pathogenesis, prevention measures, as well as pre-hospital and in-hospital treatment plans for heatstroke in children.

Validation of upper thermal thresholds for outdoor sports using thermal physiology modelling

Thermal safety guidelines with upper thresholds aim to protect athletes' health, yet evidence-based sport-specific thresholds remain unestablished. Experimenting with athletes in severely hot conditions raises ethical concerns, so we used a thermo-physiological model to validate the thresholds of guidelines for outdoor sports. First, the reproducibility of the joint system thermoregulation model (JOS-3) of core temperature has been validated for 18 sports experiments (n = 213) and 11 general exercise experiments (n = 121) using the Bland - Altman analysis. Then, core temperatures were predicted using the JOS-3 in conditions corresponding to the upper thresholds, and if the 90th-99.7th percentile core temperature value (corresponding to 0.3%-10% of the participants) exceeded 40°C, the thresholds were judged as potentially hazardous. Finally, we proposed revisions for sports with potentially hazardous thresholds. As a result, the JOS-3 could simulate core temperature increases in most experiments (27/29) for six sports and general exercises with an accuracy of 0.5°C. The current upper thresholds for marathons, triathlons, and football are potentially hazardous. Suggested revisions, based on specified percentiles, include: Football: revise from wet bulb globe temperature (WBGT) 32°C to 29-31°C or not revise. Marathon: revise from WBGT 28°C to 24-27°C. Triathlon: revise from WBGT 32.2°C to 23-26°C. If conducting sports events under the revised upper thresholds proves difficult, taking measures for a possible high incidence of heat illness becomes crucial, such as placing additional medical resources, assisting heat acclimatization and cooling strategies for participants, and rule changes such as shorter match times and increased breaks.

Phase-change material cooling blanket: A feasible cooling choice during transport after exercise-induced hyperthermia

BACKGROUND

Exercise-induced hyperthermia preceding the onset of exertional heatstroke requires a rapid reduction in the body core temperature (T_core) to ensure safety. In recent years, phase-change material (PCM) cooling devices have been increasingly used for rapid cooling after hyperthermia due to their superior capacity for heat absorption.

OBJECTIVES

This study aimed to evaluate the cooling performance and effectiveness of a PCM cooling blanket on heart rate (HR) and heart rate variability (HRV) recovery after exercise-induced hyperthermia.

DESIGN

Randomized cross-over.

METHODS

The study participants were 12 male volunteers who were engaged in professional training and completed an endurance exercise for approximately 30 min in a hot and humid environment (temperature ≈ 30 °C; relative humidity ≈ 66%). The participants underwent a 30-min cooling trial after exercise, receiving either treatment with a PCM cooling blanket (PCM group) or natural cooling (CON group). The T_core, HR, and HRV time-domain indices were used for analysis.

RESULTS

The T_core values were significantly lower in the PCM group during cooling. Reductions in the T_core from precooling to 20 min of cooling were significantly greater in the PCM group than in the CON group. The HR in the PCM group was lower than that recorded in the CON group at 10 and 20 min of cooling. The reduction in HR during cooling from precooling was also significantly greater in the PCM group. HRV time-domain indices during cooling in the PCM group were significantly lower compared with the CON group while elevations in some HRV time-domain indices from precooling to postcooling were significantly greater in the PCM group than in the CON group.

CONCLUSIONS

The PCM cooling blanket had good cooling performance and the ability to hasten recovery of both HR and HRV. It may serve as a feasible cooling choice during transport after exercise-induced hyperthermia.

Rectal Temperature Cooling Using 2 Cold-Water Immersion Preparation Strategies

CONTEXT

Cold-water immersion (CWI) is essential to treat patients with exertional heatstroke (EHS). Experts recommend that patients with EHS be immersed in water between 1.7°C and 15°C within 30 minutes of collapse. Some clinicians fill cooling tubs several hours before exercise, keep the tub in hot conditions, and then add ice in the event of an EHS emergency. No data exist on whether adding ice to water at the time of treatment is as effective as keeping water in the recommended range.

OBJECTIVES

To (1) compare the cooling rates of individuals immersed in a water bath kept at 10°C (CON) or 17°C water with 75.7 L (20 gal) of ice added to it immediately upon immersion (ICE) and (2) examine perceptual responses before, during, and after cooling.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twelve individuals (7 men, 5 women; age = 22 ± 2 years, height = 176.0 ± 12.8 cm, mass = 74.5 ± 10.6 kg).

INTERVENTIONS

Participants exercised in the heat until rectal temperature was 39.5°C. They then immersed themselves in CON (initial water volume = 681 ± 7.6 L, 10.0°C ± 0.03°C) or ICE (initial water volume = 605.7 ± 7.6 L water at 17.0°C ± 0.03°C with 75.7 L ice) until rectal temperature was 38°C. Thermal sensation and environmental symptoms questionnaire (ESQ) responses were recorded before, during, and after exercise and cooling.

MAIN OUTCOME MEASURE(S)

Rectal temperature cooling rates, thermal sensation, ESQ responses.

RESULTS

Participants exercised for similar durations (CON = 39.6 ± 18.2 minutes, ICE = 38.8 ± 14.3 minutes, Z11 = 0.94, P = .38) and had similar thermal sensation and ESQ scores immediately postexercise each day (P values > .05). They cooled quickly and at similar rates in both conditions (CON = 0.20°C ± 0.06°C/min, ICE = 0.21°C ± 0.12°C/min, t12 = 0.72, P = .49). Perception data were similar between conditions during and after cooling (P < .05).

CONCLUSIONS

Clinicians can cool patients with EHS quickly by adding ice to water that has warmed to above expert recommendations. Adding ice to a water bath at the time of EHS emergencies could save time, energy, and resources instead of always maintaining water bath temperatures within expert-recommended ranges.

Excellent Rectal Temperature Cooling Rates in the Polar Life Pod Consistent With Stationary Tubs

CONTEXT

Several tools exist to reduce rectal temperature (TREC) quickly for patients experiencing exertional heatstroke (EHS). Stationary tubs effectively treat EHS but are bulky and impractical in some situations. More portable cold-water immersion techniques, such as tarp-assisted cooling with oscillation, are gaining popularity because of their benefits (eg, less water needed, portability). The Polar Life Pod (PLP) may be another portable way to reduce TREC, but few researchers have examined its effectiveness.

OBJECTIVES

To determine whether the PLP and stationary tub reduced TREC at acceptable or ideal rates, whether TREC cooling rates differed by method, and how participants felt before, during, and after cooling.

DESIGN

Randomized crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirteen individuals (8 men, 5 women; age = 21 ± 2 years, mass = 73.99 ± 11.24 kg, height = 176.2 ± 11.1 cm).

INTERVENTION(S)

Participants exercised in the heat until TREC was 39.5°C. They immersed themselves in either the PLP (202.7 ± 23.8 L, 3.2 ± 0.6°C) or a stationary tub (567.8 ± 7.6 L, 15.0 ± 0.1°C) until TREC was 38°C. Thermal sensation and environmental symptom questionnaire (ESQ) responses were recorded before, during, and after exercise and cooling.

MAIN OUTCOME MEASURE(S)

Rectal temperature cooling rates, thermal sensation, and ESQ responses.

RESULTS

Participants had similar exercise durations (PLP = 41.6 ± 6.9 minutes, tub = 42.2 ± 9.3 minutes, t12 = 0.5, P = .31), thermal sensation scores (PLP = 7.0 ± 0.5, tub = 7.0 ± 0.5, P > .05), and ESQ scores (PLP = 25 ± 13, tub = 29 ± 14, P > .05) immediately postexercise each day. Although TREC cooling rates were excellent in both conditions, the PLP cooled faster than the stationary tub (PLP = 0.28 ± 0.09°C/min, tub = 0.20 ± 0.09°C/min, t12 = 2.5, P = .01). Thermal sensation in the PLP condition was lower than that in the tub condition halfway through cooling (PLP = 1 ± 1, tub = 2 ± 1, P < .05) and postcooling (PLP = 2 ± 1, tub = 3 ± 1, P < .05). The ESQ scores were higher for PLP than for the stationary tub postcooling (PLP = 25 ± 14, tub = 12 ± 9, P < .05).

CONCLUSIONS

The PLP and the stationary tub cooled individuals with hyperthermia at ideal rates for treating patients with EHS (ie, >0.16°C/min). The PLP may be an effective tool for treating EHS when limited water volumes and portability are concerns. Clinicians should have rewarming tools and strategies (eg, heating blankets) available to improve patients' comfort after PLP use.

Cooling Modality Effectiveness and Mortality Associate With Prehospital Care of Exertional Heat Stroke Casualities

BACKGROUND

Cold-water immersion is the gold standard for field treatment of an exertional heat stroke (EHS) casualty. Practical limitations may preclude this method and ice sheets (bed linens soaked in ice water) have emerged as a viable alternative. Laboratory studies suggest that this is an inferior method; however, the magnitude of hyperthermia is limited and may underestimate the cooling rate in EHS casualties.

OBJECTIVE

Our aim was to determine the prehospital core cooling rate, need for continued cooling on arrival to the emergency department, and mortality rate associated with ice sheet use.

METHODS

De-identified retrospective data were obtained from emergency medical services (EMS) and included presence or absence of altered mental status, cooling measures applied prior to EMS arrival, and time and core temperature (T_c; rectal) on-scene and on hospital arrival. Cooling rate was calculated from time and temperature data. Mortality data were obtained from the U.S. Army Combat Readiness Center.

RESULTS

There were 462 casualties that met inclusion criteria. The cooling rate for the entire sample was 0.07°C ± 0.08°C · min^-1. EHS casualties with an observed initial T_c < 39°C had an en route cooling rate of 0.03°C ± 0.04°C · min^-1 vs. initial T_c ≥ 39°C cooling rate of 0.16°C ± 0.08°C · min^-1. There was one fatality due to EHS, for a mortality rate of 0.20% (95% CI 0.01-1.20%).

CONCLUSIONS

The cooling rate in EHS casualties with initial T_c ≥ 39°C was approximately double that reported in laboratory studies. The observed mortality rate was comparable with casualties treated with cold-water immersion. Our data suggest that ice sheets provide a viable alternative when practical constraints preclude cold-water immersion.

Treating exertional heat stroke: Limited understanding of the female response to cold water immersion

According to an expansive body of research and best practice statements, whole-body cold water immersion is the gold standard treatment for exertional heat stroke. However, as this founding evidence was predominantly drawn from males, the current guidelines for treatment are being applied to women without validation. Given the recognised differences in thermal responses experienced by men and women, all-encompassing exertional heat stroke treatment advice may not effectively protect both sexes. In fact, recent evidence suggests that hyperthermic women cool faster than hyperthermic men during cold water immersion. This raises the question of whether overcooling is risked if the present guidelines are followed. The current mini-review examined the literature on women's response to cold water immersion as a treatment for exertional heat stroke and aimed to clarify whether the current guidelines have appropriately considered research investigating women. The potential implications of applying these guidelines to women were also discussed.

Wearable Sensor Technology to Predict Core Body Temperature: A Systematic Review

Heat-related illnesses, which range from heat exhaustion to heatstroke, affect thousands of individuals worldwide every year and are characterized by extreme hyperthermia with the core body temperature (CBT) usually > 40 °C, decline in physical and athletic performance, CNS dysfunction, and, eventually, multiorgan failure. The measurement of CBT has been shown to predict heat-related illness and its severity, but the current measurement methods are not practical for use in high acuity and high motion settings due to their invasive and obstructive nature or excessive costs. Noninvasive predictions of CBT using wearable technology and predictive algorithms offer the potential for continuous CBT monitoring and early intervention to prevent HRI in athletic, military, and intense work environments. Thus far, there has been a lack of peer-reviewed literature assessing the efficacy of wearable devices and predictive analytics to predict CBT to mitigate heat-related illness. This systematic review identified 20 studies representing a total of 25 distinct algorithms to predict the core body temperature using wearable technology. While a high accuracy in prediction was noted, with 17 out of 18 algorithms meeting the clinical validity standards. few algorithms incorporated individual and environmental data into their core body temperature prediction algorithms, despite the known impact of individual health and situational and environmental factors on CBT. Robust machine learning methods offer the ability to develop more accurate, reliable, and personalized CBT prediction algorithms using wearable devices by including additional data on user characteristics, workout intensity, and the surrounding environment. The integration and interoperability of CBT prediction algorithms with existing heat-related illness prevention and treatment tools, including heat indices such as the WBGT, athlete management systems, and electronic medical records, will further prevent HRI and increase the availability and speed of data access during critical heat events, improving the clinical decision-making process for athletic trainers and physicians, sports scientists, employers, and military officers.

Biomarkers of heatstroke-induced organ injury and repair

NEW FINDINGS

What is the topic of this review? The status and potential role of novel biological markers (biomarkers) that can help identify the patients at risk of organ injury or long-term complications following heatstroke. What advances does it highlight? Numerous biomarkers were identified related to many aspects of generalized heatstroke-induced cellular injury and tissue damage, and heatstroke-provoked cardiovascular, renal, cerebral, intestinal and skeletal muscle injury. No novel biomarkers were identified for liver or lung injury.

ABSTRACT

Classic and exertional heatstroke cause acute injury and damage across numerous organ systems. Moreover, heatstroke survivors may sustain long-term neurological, cardiovascular and renal complications with a persistent risk of death. In this context, biomarkers, defined as biological samples obtained from heatstroke patients, are needed to detect early organ injury, and predict outcomes to develop novel organ preservation therapeutic strategies. This narrative review provides preliminary insights that will guide the development and future utilization of these biomarkers. To this end, we have identified numerous biomarkers of widespread heatstroke-associated cellular injury, tissue damage and repair (extracellular heat shock proteins 72 and 60, high mobility group box protein 1, histone H3, and interleukin-1α), and other organ-specific biomarkers including those related to the cardiovascular system (cardiac troponin I, endothelium-derived factors, circulation endothelial cells, adhesion molecules, thrombomodulin and von Willebrand factor antigen), the kidneys (plasma and urinary neutrophil gelatinase-associated lipocalin), the intestines (intestinal fatty acid-binding protein 2), the brain (serum S100β and neuron-specific enolase) and skeletal muscle (creatine kinase, myoglobin). No specific biomarkers have been identified so far for liver or lung injury in heatstroke. Before translating the identified biomarkers into clinical practice, additional preclinical and clinical prospective studies are required to further understand their clinical utility, particularly for the biomarkers related to long-term post-heatstroke health outcomes.

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.

Efficiency of three cooling methods for hyperthermic military personnel linked to water availability

PURPOSE

Three feasible cooling methods for treatment of hyperthermic individuals in the military, that differed considerably in water volume needed (none to ~80 L), were evaluated.

METHODS

Ten male soldiers were cooled following exercise-induced hyperthermia (rectal temperature (T_re) ∼39.5 °C) using ventilation by fanning (1.7 m s^-1), ventilation by fanning (1.7 m s^-1) while wearing a wet t-shirt (250 mL-27 °C water) and tarp assisted cooling with oscillations (80 L of 27.2 ± 0.5 °C water; TACO).

RESULTS

Cooling rates were higher using TACO (0.116 ± 0.032 °C min^-1) compared to ventilation (0.065 ± 0.011 °C min^-1, P<0.001) and ventilation in combination with a wet t-shirt (0.074 ± 0.020 °C min^-1, P=0.002). Time to cool (TTC) to T_re=38.2 °C for TACO was shorter (14 ± 4 min) compared to ventilation only (20 ± 5 min; P=0.018), but not to ventilation while wearing a wet t-shirt (18 ± 6 min; P=0.090).

CONCLUSIONS

TACO may be an acceptable, efficient and feasible cooling method in case of exertional heat stroke. However, in case of limited water availability, transportat should be prioritized, and cooling of any form should be implemented while waiting for and during transport.

Exertional heat stroke: An evidence based approach to clinical assessment and management

NEW FINDINGS

What is the topic of this review? The treatment of exertional heat stress, from initial field care through the return-to-activity decision, is reviewed. What advances does it highlight? Clinical assessment during field care using AVPU and vital signs to gauge recovery Approaches to field cooling and end of active cooling Shared clinical decision making for return to activity recommendations ABSTRACT: Exertional heat stroke (EHS) is a potentially fatal condition characterized by central nervous system dysfunction and body temperature often but not always >40°C that occurs in the context of physical work in warm or hot environments. In this paper, we review the continuum of care, from initial recognition and field care to transport and hospital care, and finally return to duty considerations. Morbidity and mortality can be greatly reduced if not eliminated with prompt recognition and aggressive cooling. If medical personnel are not present at point of collapse during or immediately following exercise, EHS should be the presumptive diagnosis until a formal diagnosis can be determined by qualified medical staff. EHS is the rare medical situation where initial treatment (cooling) takes precedence over transport to a medical facility, where advanced medical care may be required for severe EHS casualties. Recovery from EHS and return to activity is usually straightforward and unremarkable provided the casualty is rapidly cooled at time of collapse and adequate time is allowed for body healing. However, evidence-based data to guide return to activity following EHS is limited. Current research suggests that most individuals recover completely within a few weeks though some individuals may suffer prolonged sequalae and additional evaluation may be warranted, including heat tolerance testing. Several aspects of the care of the EHS casualty are based on best practices derived from personal experience and continued research is necessary to optimize evaluation and management. This article is protected by copyright. All rights reserved.

Proper Recognition and Management of Exertional Heat Stroke in a High School Cross-Country Runner: A Validation Clinical Case Report

A 14-year-old female high school cross- country runner (height = 154 cm, mass = 48.1 kg) with no history of exertional heat stroke (EHS) collapsed at the end of a race. An athletic trainer assessed the patient, who presented with difficulty breathing and then other signs of EHS (eg, confusion and agitation). The patient was taken to the medical area and draped with a towel, and a rectal temperature (Tre) of 106.9°F (41.6°C) was obtained. The emergency action plan was activated, and emergency medical services was called. The patient was submerged in a cold-water immersion tub until emergency medical services arrived (∼15 minutes; Tre = 100.1°F; cooling rate: 0.41°F.min-1[0.25°C.min-1]). At the hospital, the patient received intravenous fluids, and urine and blood tests were normal. She was not admitted and returned to running without sequelae. Following best practices, secondary school athletic trainers can prevent deaths from EHS by properly recognizing the condition and providing rapid cooling before transport.

Prehospital management of exertional heat stroke at sports competitions for Paralympic athletes

OBJECTIVES

To adapt key components of exertional heat stroke (EHS) prehospital management proposed by the Intenational Olympic Committee Adverse Weather Impact Expert Working Group for the Olympic Games Tokyo 2020 so that it is applicable for the Paralympic athletes.

METHODS

An expert working group representing members with research, clinical and lived sports experience from a Para sports perspective reviewed and revised the IOC consensus document of current best practice regarding the prehospital management of EHS.

RESULTS

Similar to Olympic competitions, Paralympic competitions are also scheduled under high environmental heat stress; thus, policies and procedures for EHS prehospital management should also be established and followed. For Olympic athletes, the basic principles of EHS prehospital care are: early recognition, early diagnosis, rapid, on-site cooling and advanced clinical care. Although these principles also apply for Paralympic athletes, slight differences related to athlete physiology (eg, autonomic dysfunction) and mechanisms for hands-on management (eg, transferring the collapsed athlete or techniques for whole-body cooling) may require adaptation for care of the Paralympic athlete.

CONCLUSIONS

Prehospital management of EHS in the Paralympic setting employs the same procedures as for Olympic athletes with some important alterations.

Athlete Medical Services at the Marathon and Race Walking Events During Tokyo 2020 Olympics

Epidemiological data from race walk and marathon events suggest that a high incidence rate of exertional heat illness is associated with high ambient temperature and relative humidity. The 2020 Summer Olympics in Tokyo was no exception, which led the organizing committee to relocate the race walk and marathon competitions to Sapporo, which was predicted to experience much milder heat. Nonetheless, during the Games, Sapporo recorded the highest daytime ambient temperature in the past 97 years, with consecutive days over 30°C from July 22nd to August 7th, 2021. Five events (men's and women's 20 km race walk, men's 50 km race walk, women's and men's marathon) were held in Sapporo from August 5th to August 8th, 2021. The percentage of athletes who did not finish (DNF) in each event was 8.8% in men's 20 km race walk, 20.3% in men's 50 km race walk, 8.6% in women's 20 km race walk, 17.1% in women's marathon and 28.3% in men's marathon. A total of fifty athletes were transferred to the athlete medical station: 28 athletes completed the race (i.e., collapsed after finish line), while 24 were DNF athletes transported from the course. Forty-eight (96%) of athletes who were admitted to the athlete medical station exhibited signs and symptoms of exertional heat illness. Two athletes diagnosed with exertional heat stroke and three athletes diagnosed with severe heat exhaustion (rectal body temperature >39.5°C with or without central nervous system disturbance) were cooled using whole-body cold water immersion at the heat deck located within the athlete medical station. All athletes who were cooled successfully recovered without any complications. These athletes required an average of 14 ± 9.4 min (range, 6–30 min) to cool their rectal temperature below 39°C. These results show the importance for event organizers to prepare strategies to keep athletes cool, such as an ample amount of ice and water to supply whole-body cold water immersion.

Body Anthropometrics and Rectal Temperature Cooling Rates in Women With Hyperthermia

CONTEXT

Cold-water immersion (CWI) is the best treatment for exertional heat stroke (EHS), and rectal temperature (Trec) cooling rates may differ between sexes. Previous authors have suggested body surface area (BSA) to lean body mass (LBM) ratio is the largest factor affecting CWI Trec cooling rates in men with hyperthermia; this has never been confirmed in women with hyperthermia.

OBJECTIVE

To examine whether the BSA:LBM ratio and other anthropometrics affect Trec cooling rates in women with hyperthermia.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Sixteen women were placed in either a low BSA:LBM ratio (LOW; n = 8; age = 22 ± 1 years, height = 166.8 ± 6.0 cm, mass = 64.1 ± 4.5 kg, BSA:LBM ratio = 3.759 ± 0.214 m2/kg·102) or high BSA:LBM ratio group (HIGH; n = 8; age = 22 ± 2 years, height = 162.7 ± 8.9 cm, mass = 65.8 ± 12.7 kg, BSA:LBM ratio = 4.161 ± 0.232 m2/kg·102).

INTERVENTION(S)

On day 1, we measured physical characteristics using dual-energy x-ray absorptiometry, and participants completed a maximal oxygen consumption test. On day 2, participants walked at 4.8 km/h for 3 minutes and then ran at 80% of their predetermined maximal oxygen consumption for 2 minutes in the heat (temperature = ~40°C, relative humidity = 40%). This sequence was repeated until Trec reached 39.5°C. Then, they completed CWI (temperature = ~10°C) until Trec was 38°C.

MAIN OUTCOME MEASURE(S)

Rectal temperature and CWI cooling rates.

RESULTS

Groups had different BSA:LBM ratios (P = .001), body fat percentages (LOW: 25.7% ± 5.0%; HIGH: 33.7% ± 6.3%; P = .007), and LBM (LOW: 45.8 ± 3.0 kg; HIGH: 41.0 ± 5.1 kg; P = .02) but not different BSA (LOW: 1.72 ± 0.08 m2; HIGH: 1.70 ± 0.16 m2; P = .40) or BMI (LOW: 23.1 ± 2.1; HIGH: 24.9 ± 4.7; P = .17). Despite differences in several physical characteristics, Trec cooling rates were excellent but comparable (LOW: 0.26°C/min ± 0.09°C/min; HIGH: 0.27°C/min ± 0.07°C/min; P = .39). The BSA:LBM ratio (r = 0.14, P = .59), body fat percentage (r = 0.29, P = .28), LBM (r = -0.10, P = .70), BSA (r = -0.01, P = .97), and BMI (r = 0.37, P = .16) were not correlated with Trec cooling rates.

CONCLUSIONS

Body anthropometrics did not affect CWI Trec cooling rates in women with hyperthermia. Clinicians need not worry about anthropometric characteristics slowing the treatment of severe hyperthermia in women using CWI.

Classic and exertional heatstroke

In the past two decades, record-breaking heatwaves have caused an increasing number of heat-related deaths, including heatstroke, globally. Heatstroke is a heat illness characterized by the rapid rise of core body temperature above 40 °C and central nervous system dysfunction. It is categorized as classic when it results from passive exposure to extreme environmental heat and as exertional when it develops during strenuous exercise. Classic heatstroke occurs in epidemic form and contributes to 9-37% of heat-related fatalities during heatwaves. Exertional heatstroke sporadically affects predominantly young and healthy individuals. Under intensive care, mortality reaches 26.5% and 63.2% in exertional and classic heatstroke, respectively. Pathological studies disclose endothelial cell injury, inflammation, widespread thrombosis and bleeding in most organs. Survivors of heatstroke may experience long-term neurological and cardiovascular complications with a persistent risk of death. No specific therapy other than rapid cooling is available. Physiological and morphological factors contribute to the susceptibility to heatstroke. Future research should identify genetic factors that further describe individual heat illness risk and form the basis of precision-based public health response. Prioritizing research towards fundamental mechanism and diagnostic biomarker discovery is crucial for the design of specific management approaches.

Gait instability and estimated core temperature predict exertional heat stroke

OBJECTIVE

Exertional heat stroke (EHS), characterised by a high core body temperature (Tcr) and central nervous system (CNS) dysfunction, is a concern for athletes, workers and military personnel who must train and perform in hot environments. The objective of this study was to determine whether algorithms that estimate Tcr from heart rate and gait instability from a trunk-worn sensor system can forward predict EHS onset.

METHODS

Heart rate and three-axis accelerometry data were collected from chest-worn sensors from 1806 US military personnel participating in timed 4/5-mile runs, and loaded marches of 7 and 12 miles; in total, 3422 high EHS-risk training datasets were available for analysis. Six soldiers were diagnosed with heat stroke and all had rectal temperatures of >41°C when first measured and were exhibiting CNS dysfunction. Estimated core temperature (ECTemp) was computed from sequential measures of heart rate. Gait instability was computed from three-axis accelerometry using features of pattern dispersion and autocorrelation.

RESULTS

The six soldiers who experienced heat stroke were among the hottest compared with the other soldiers in the respective training events with ECTemps ranging from 39.2°C to 40.8°C. Combining ECTemp and gait instability measures successfully identified all six EHS casualties at least 3.5 min in advance of collapse while falsely identifying 6.1% (209 total false positives) examples where exertional heat illness symptoms were neither observed nor reported. No false-negative cases were noted.

CONCLUSION

The combination of two algorithms that estimate Tcr and ataxic gate appears promising for real-time alerting of impending EHS.

No protective benefits of low dose acute L-glutamine supplementation on small intestinal permeability, epithelial injury and bacterial translocation biomarkers in response to subclinical exertional-heat stress: A randomized cross-over trial

Exertional heat stress disrupts gastrointestinal permeability and, through subsequent bacterial translocation, can result in potentially fatal exertional heat stroke. Glutamine supplementation is a potential countermeasure although previously validated doses are not universally well tolerated. Ten males completed two 80-minute subclinical exertional heat stress tests (EHSTs) following either glutamine (0.3 g kg FFM^-1) or placebo supplementation. Small intestinal permeability was assessed using the lactulose/rhamnose dual sugar absorption test and small intestinal epithelial injury using Intestinal Fatty-Acid Binding Protein (I-FABP). Bacterial translocation was assessed using the total 16S bacterial DNA and Bacteroides/total 16S DNA ratio. The glutamine bolus was well tolerated, with no participants reporting symptoms of gastrointestinal intolerance. Small intestinal permeability was not influenced by glutamine supplementation (p = 0.06) although a medium effect size favoring the placebo trial was observed (d = 0.73). Both small intestinal epithelial injury (p < 0.01) and Bacteroides/total 16S DNA (p = 0.04) increased following exertional heat stress, but were uninfluenced by glutamine supplementation. Low-dose acute oral glutamine supplementation does not protect gastrointestinal injury, permeability, or bacterial translocation in response to subclinical exertional heat stress.

Exertional heat stroke: pathophysiology and risk factors

Exertional heat stroke, the third leading cause of mortality in athletes during physical activity, is the most severe manifestation of exertional heat illnesses. Exertional heat stroke is characterised by central nervous system dysfunction in people with hyperthermia during physical activity and can be influenced by environmental factors such as heatwaves, which extend the incidence of exertional heat stroke beyond athletics only. Epidemiological data indicate mortality rates of about 27%, and survivors display long term negative health consequences ranging from neurological to cardiovascular dysfunction. The pathophysiology of exertional heat stroke involves thermoregulatory and cardiovascular overload, resulting in severe hyperthermia and subsequent multiorgan injury due to a systemic inflammatory response syndrome and coagulopathy. Research about risk factors for exertional heat stroke remains limited, but dehydration, sex differences, ageing, body composition, and previous illness are thought to increase risk. Immediate cooling remains the most effective treatment strategy. In this review, we provide an overview of the current literature emphasising the pathophysiology and risk factors of exertional heat stroke, highlighting gaps in knowledge with the objective to stimulate future research.

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.” 

Association between active cooling and lower mortality among patients with heat stroke and heat exhaustion

Body cooling is recommended for patients with heat stroke and heat exhaustion. However, differences in the outcomes of patients who do or do not receive active cooling therapy have not been determined. The best available evidence supporting active cooling is based on a case series without comparison groups; thus, the effectiveness of this method in improving patient prognoses cannot be appropriately quantified. Therefore, we compared the outcomes of heat stroke patients receiving active cooling with those of patients receiving rehydration-only therapy. This prospective observational multicenter registry-based study of heat stroke and heat exhaustion patients was conducted in Japan from 2010 to 2019. The patients were stratified into the "severe" group or the "mild-to-moderate" group, per clinical findings on admission. After conducting multivariate logistic regression analyses, we compared the prognoses between patients who received "active cooling + rehydration" and patients who received "rehydration only," with in-hospital death as the endpoint. Sex, age, onset situation (i.e., exertional or non-exertional), core body temperature, liver damage, renal dysfunction, and disseminated intravascular coagulation were considered potential covariates. Among those who received active cooling and rehydration-only therapy, the in-hospital mortality rates were 21.5% and 35.5%, respectively, for severe patients (n = 231) and 3.9% and 5.7%, respectively, for mild-to-moderate patients (n = 578). Rehydration-only therapy was associated with a higher in-hospital mortality in patients with severe heat illness (adjusted odds ratio [aOR], 3.29; 95% confidence interval [CI], 1.21-8.90), whereas the cooling methods were not associated with lower in-hospital mortality in patients with mild-to-moderate heat illness (aOR, 2.22; 95% CI, 0.92-5.84). Active cooling was associated with lower in-hospital mortality only in the severe group. Our results indicated that active cooling should be recommended as an adjunct to rehydration-only therapy for patients with severe heat illness.

Burden of Injury and Illness in the Road Race Medical Tent: A Narrative Review

OBJECTIVE

To summarize the literature relating to prehospital care at 5 km through marathon distance road races and present the epidemiology of common medical encounters, significant medical complications, and medical outcomes.

DATA SOURCES

We searched PubMed and Google Scholar for the published literature pertaining to road race medical tent encounters at 5 km through marathon distance road races from 2000 to 2018. We included English-language, original articles reporting on injury and illness incidence.

MAIN RESULTS

Standard medical encounter definitions have recently been formulated in response to the previous lack of uniform definitions. The incidence of medical complications at road races may be influenced by environmental conditions and race distance. Minor and moderate medical encounters, such as dermatologic injuries, musculoskeletal injuries, and exercise-associated collapse, are common. Serious and life-threatening medical complications, including exertional heat stroke, exercise-associated hyponatremia, and cardiac arrest, are less frequent. Fatalities are also rare, with rates of 0.3 to 5 per 100 000 participants reported at marathons. The ratio of hospital transports to medical encounters is low.

CONCLUSIONS

On-site medical services play a key role in the safety of both runners and the community. Future research and care initiatives in this field should focus on optimizing treatment protocols, promoting injury prevention efforts and reducing host community costs.

Exertional heat stroke with reversible severe cerebral edema

Severe cerebral edema associated with exertional heat stroke is a major cause of death or disability. However, few studies on severe cerebral edema resulting from heat stroke have reported neuroradiological findings. Moreover, all the patients in these previous reports either died or remained severely disabled. Here, we report a case of exertional heat stroke with severe cerebral edema that probably developed or worsened due to delayed body temperature normalization. In contrast to previous reports, the patient showed complete clinical and neuroradiological recovery. This rare case suggests that severe cerebral edema could be reversed through meticulous supportive management. Moreover, it confirms the importance of rapid and effective cooling in heat stroke treatment.

High Schools' Adoption of Evidence-Based Practices for the Management of Exertional Heat Stroke

CONTEXT

Exertional heat stroke (EHS) deaths can be prevented by adhering to best practices.

OBJECTIVE

To investigate high schools' adoption of policies and procedures for recognizing and treating patients with EHS and the factors influencing the adoption of a comprehensive policy.

DESIGN

Cross-sectional study.

SETTING

Online questionnaire.

PATIENTS OR OTHER PARTICIPANTS

Athletic trainers (ATs) practicing in the high school (HS) setting.

MAIN OUTCOME MEASURE(S)

Using the National Athletic Trainers' Association position statement on exertional heat illness, we developed an online questionnaire and distributed it to ATs to ascertain their schools' current written policies for using rectal temperature and cold-water immersion. The precaution adoption process model allowed for responses to be presented across the various health behavior stages (unaware if have the policy, unaware of the need for the policy, unengaged, undecided, decided not to act, decided to act, acting, and maintaining). Additional questions addressed perceptions of facilitators and barriers. Data are presented as proportions.

RESULTS

A total of 531 ATs completed the questionnaire. Overall, 16.9% (n = 62) reported adoption of all components for the proper recognition and treatment of EHS. The component with the highest adoption level was "cool first, transport second"; 74.1% (n = 110) of ATs described acting on or maintaining the policy. The most variability in the precaution adoption process model responses was for a rectal temperature policy; 28.7% (n = 103) of ATs stated they decided not to act and 20.1% (n = 72) stated they maintained the policy. The most frequently cited facilitator of and barrier to obtaining rectal temperature were a mandate from the state HS athletics association (n = 274, 51.5%) and resistance to or apprehension of parents or legal guardians (n = 311, 58.5%), respectively.

CONCLUSIONS

Athletic trainers in the HS setting appeared to be struggling to adopt a comprehensive EHS strategy, with rectal temperature continuing as the biggest challenge. Tailored strategies based on health behavior, facilitators, and barriers may aid in changing this paradigm.

ACSM Expert Consensus Statement on Exertional Heat Illness: Recognition, Management, and Return to Activity

ABSTRACT

Exertional heat stroke (EHS) is a true medical emergency with potential for organ injury and death. This consensus statement emphasizes that optimal exertional heat illness management is promoted by a synchronized chain of survival that promotes rapid recognition and management, as well as communication between care teams. Health care providers should be confident in the definitions, etiologies, and nuances of exertional heat exhaustion, exertional heat injury, and EHS. Identifying the athlete with suspected EHS early in the course, stopping activity (body heat generation), and providing rapid total body cooling are essential for survival, and like any critical life-threatening situation (cardiac arrest, brain stroke, sepsis), time is tissue. Recovery from EHS is variable, and outcomes are likely related to the duration of severe hyperthermia. Most exertional heat illnesses can be prevented with the recognition and modification of well-described risk factors ideally addressed through leadership, policy, and on-site health care.

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

PURPOSE

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.

METHODS

We analyzed participant characteristics, environmental data, and EHS medical encounters during the 2015-2019 Boston Marathon races.

RESULTS

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.

CONCLUSIONS

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.