Prevention

The first step in EHS management is prevention. Prevention strategies can be classified into those that can help, first, to identify and, second, to reduce risks. For example, preseason screening such as what occurs during an athlete’s pre-participation examination and daily wellness logs can identify intrinsic risk factors that are associated with EHS, such as a history of exertional heat illness, poor fitness level, lack of heat acclimatization, dehydration, recent illness, level of fatigue, and sleep deprivation [2]. Athletes and parents (if the athletes are minors) have the responsibility to report accurate information about their health status so that appropriate risk mitigation plans can be implemented. Such plans include selecting exercise that matches one’s physical fitness, implementing a team-wide heat acclimatization program, providing unlimited access to water to maintain proper hydration, and promoting adequate recovery before sport participation [1, 11]. When risk factors are known, qualified on-site medical personnel (e.g., athletic trainer, physiotherapist) and coaches also have the duties to share the information among each other so that informed decisions can be made when programming exercise mode, duration and intensity. It has been suggested that the presence of multiple risk factors heightens the risk of EHS [12]. Therefore, addressing as many modifiable risk factors identified in the preseason screening and daily wellness logs can be considered as the first line of defense in EHS prevention. A summary of existing literature about risk factors of EHS is further discussed in Chap. 3.

Environmental monitoring can also help identify EHS risk, where studies have shown increased prevalence of EHS fatalities when the environmental conditions are uncharacteristically hot for that specific region [13, 14]. These data support the use of injury surveillance and daily environmental monitoring as tools to determine high risk days for EHS, which can be led by coaches and athletic trainers. They should also determine the level of physical activity according to the wet-bulb globe temperature (WBGT) , an index used to quantify the amount of environmental heat stress by incorporating the influence from solar radiation, air temperature, humidity, and wind speed [11, 14]. It is also important for administrators to reinforce WBGT-based activity modification guidelines to support decisions for shortening or cancelling of physical activity during extreme heat as these decisions can become hard for coaches in the face of competitive athleticism.

Methods that can directly reduce the risk of EHS include heat acclimatization and body cooling [2, 15–18]. Qualified on-site medical personnel should exercise due diligence to educate the benefits and importance of these methods to coaches and administrators to receive organizational support. In order to purposefully induce heat acclimatization, a heat acclimatization program must be incorporated within the training periodization to ensure that adequate amount of stress is applied to induce physiological adaptations. In the United States, an Inter-Association Task Force released a set of evidence-based guidelines regarding heat acclimatization in 2009, with the aim to reduce exertional heat illness risk during the summer months, particularly in the American football [19]. Since its introduction, eight states have mandated the implementation of preseason heat acclimatization in secondary school American football, which resulted in a 55% reduction in exertional heat illness (95% confidence interval: 13, 77%) [18]. Heat acclimatization process generally takes 10–14 days [17] and is recommended to be conducted during preseason (i.e., early spring or summer) to allow for gradual progression in physical and thermal loads placed on the body [20]. Heat acclimatization is also a useful method to prepare athletes who have scheduled competitions in regions where the weather conditions are warmer than their home. This not only helps reduce the risk of EHS but also optimizes athletic performance in heat [21].

Pre- (i.e., before activity) and per-cooling (i.e., during activity) are other useful methods to reduce the risk of EHS by directly lowering one’s baseline internal body temperature prior to activity or by attenuating the rise in body temperature during activity, respectively [2, 15]. Since practical cooling strategies vary by setting and sport (i.e., American football is equipment laden but has unlimited number of substitutions, while soccer has a no re-entry rule for substitutions, limiting the opportunity for cooling during pregame and during halftime) [16], it is necessary for coaches and medical personnel to evaluate cooling methods that can be implemented readily. Lastly, it is important to educate coaches about the ergogenic benefits of heat acclimatization for enhancing cardiovascular fitness [17] and body cooling for endurance performance [21]. Coaches should realize that performance optimization in the heat can simultaneously facilitate EHS prevention and performance enhancement.

Pre-hospital Care

When EHS occurs, despite aforementioned prevention efforts, rapid recognition, rapid assessment, and rapid cooling must be carried out to avoid poor prognosis (see Fig. 9.1). Ideally, the pre-hospital care of EHS patients in athletics settings should be led by qualified medical personnel, such as an athletic trainer, as they are trained to recognize early signs and symptoms of EHS, use rectal thermometry to obtain an accurate internal body temperature, and administer cold water immersion to rapidly cool the body below 39 °C while continuously monitoring the internal body temperature [1]. When these steps are followed within the first 30 minutes of collapse, prognosis from EHS is promising [9]. Proper recognition and length of whole-body cooling rely on an accurate temperature assessment using rectal thermometry. However, Mazerolle et al. [22] found lack of rectal thermometry usage by college and high school athletic trainers due to insecurities, organizational barriers, and lack of resources. In such cases, clinicians and administrators should realize the legal implications for not using rectal thermometry since other methods of body temperature assessment (e.g., temporal, tympanic, oral, axillary, skin temperature) have been shown to be invalid for measuring the internal body temperature in individuals during or immediately after exercise [23, 24]. Therefore, both sports medicine and administrative staff members of an athletic team need to understand the essential use of rectal thermometry to accurately diagnose EHS and properly identify the duration of treatment. Information pertaining to the pre-hospital care of EHS patients should be documented in the form of a policies and procedures manual for the sports medicine team and a site-specific emergency action plan (EAP) to effectively carry out these procedures. Policies and procedures will help establish the consensus, while the EAP provides step-by-step process to recognize the condition, to initiate the pre-hospital care, and to transfer the patient to advanced medical facility once the hypothermia has been controlled.

In the absence of athletic trainers or other qualified medical personnel, coaches must rely on context-based inference to determine the presence of EHS since they may not be qualified or trained to use rectal thermometry. For that reason, it is imperative to educate coaches about common risk factors and clinical presentation of signs and symptoms of EHS and draft an EAP for nonmedical personnel so that they can initiate appropriate first aid (i.e., body cooling) and communicate clinical presentations to EMS [25].

Transport

In-Hospital Care and Return to Physical Activity

In ideal conditions, patients will be transported to the hospital following on-site cooling. However, patients may arrive to the hospital’s emergency department (ED) by private vehicle or ambulance with little or no attempt at pre-hospital cooling. Rapid recognition, assessment, and cooling remain the priority for the ED staff. Vital signs including rectal temperature, blood pressure, heart rate, and respiratory rate should be assessed. In the acute phase, tachycardia and hyperventilation is usually observed in EHS patients. For those patients that receive pre-hospital cooling, these values may have returned to the normal range [27]. Cold water immersion in an ED may be challenging due to space and equipment (i.e., tubs, large quantities of ice and water) constraints. Other cooling modalities such as rotating ice water- soaked towels [28] or tarp-assisted cooling [29] may be substituted as effective cooling modalities.

Upon arrival to the ED, EHS patients may be dehydrated and exhibit signs of hypotension and hemoconcentration and hypercalcemia and hyperproteinemia [27]. Oral (if tolerated) or IV fluids may be necessary to restore fluid and electrolyte losses in these instances. In EHS patients, it is also not uncommon to observe a hypothermic overshoot following treatment [12]. The chance of a drastic drop in internal body temperature from pre-hospital treatment and patient’s inability to restore normal body temperature (≈36–37 °C) requires direct (e.g., rectal temperature) and continuous monitoring of internal body temperature. It should be noted that hypothermic patients may need rewarming as the ability to regulate body temperature may be altered in some patients. On the contrary, in the event that a patient’s temperature begins to rise, cooling should be re-instituted. In addition, even after the internal body temperature is stabilized, the inflammatory response and blood coagulation may continue [27]. Blood tests such as blood urea nitrogen (BUN), creatinine (Cr), creatine phosphokinase (CPK), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels should be obtained to quantify the level of muscle damage and monitor renal and liver functions, which are commonly affected in EHS patients [26, 27].

A physician may clear the athlete to low-intensity activity only when full recovery of organ function is confirmed via blood work and subjective symptoms (e.g., 7–21 days post EHS incident) [30]. The progression for return to activity should be supervised by trained personnel (e.g., team physician, primary care physician, athletic trainer, etc.), starting from low-intensity exercise in cool environment to gradually transitioning the intensity and environmental condition to mimic a traditional heat acclimatization protocol [30, 31]. Upon receiving the collapsed athlete’s permission, it is ideal for the medical records taken at the time of hospital admittance be shared with qualified medical personnel who will have daily contact with the athlete during the return to activity progression to gauge the extent of initial damage incurred by the body. When the athlete has regained adequate physical fitness and heat tolerance, a standardized heat tolerance test [30, 32] can be prescribed to assess the athlete’s ability to withstand a fixed exercise protocol in heat. Medical lab results, changes in clinical symptoms (e.g., lethargy, weakness), and heat tolerance test results should be evaluated together by the physician and/or athletic trainer, to comprehensively evaluate the athlete’s readiness to return to full activity.