EHS is diagnosed by an elevated rectal temperature ≥40°C (104°F) and associated central nervous system (CNS) dysfunction.21 EHS should be strongly suspected in any athlete exercising in heat who exhibits signs of CNS dysfunction, including disorientation, confusion, dizziness, erratic behavior, irritability, headache, loss of coordination, delirium, collapse, or seizures.7,12,15 EHS may also present with symptoms of heat exhaustion, including fatigue, hyperventilation, tachycardia, vomiting, diarrhea, and hypotension.7,12,15
Rectal temperature should be taken for any athlete with suspected EHS, as other modalities—oral, skin, axillary, and aural—can be inaccurate and easily modified by ambient confounders such as ambient and skin temperature, athlete hyperventilation, and consumption of liquids.7,11,12 Athletes exhibiting CNS symptoms with moderately elevated rectal temperatures that do not exceed 40°C should also be assumed to be suffering from EHS and treated with rapid cooling.11 On the other hand, athletes with CNS symptoms who are normothermic should be assumed to have EAH until ruled out by electrolyte assessment; IV fluids should be at no more than keep vein open (KVO) pending this determination.11 In some cases, an athlete may initially present with altered mental status but return to “normal.” However, this improvement may represent a “lucid period”; evaluation should continue with rectal temperature and treatment, as EHS in these cases may progress quickly.15
Treatment is centered on rapid, whole body cooling initiated at the first sign of heat illness.7,22 The goal of treatment is to achieve a rectal temperature <38.9°C within 30 minutes of the onset of EHS.15 Upon diagnosis, the athlete should be quickly placed in a tub of ice water to facilitate cold water immersion (CWI) therapy. Some guidelines suggest the athlete’s clothing be removed to potentiate evaporative cooling during CWI;12 however, cooling should not be delayed due to difficulties in removing equipment. CWI, where a heat stroke victim is submerged in ice water up to their neck while water is continuously circulated, is generally considered to be the gold standard treatment as it is the modality with the highest recorded cooling rates and the lowest rate of morbidity and mortality.7,20,21 Multiple studies of CWI have shown that survival nears 100% when aggressive cooling starts within 5 minutes of collapse or identification of EHS.20,21,22
If whole body CWI is unavailable, alternative methods of rapid cooling should be employed. Partial CWI, with torso immersion being preferable to the extremities, has been shown to achieve an acceptable rate of cooling to achieve sufficient drops in internal body temperature.20,23 However, one popular treatment—applying ice packs to the whole body, in particular to the groin and axillae—has not been shown to be sufficient to achieve standard cooling goals.20 None of these methods have been shown to be as effective as CWI.23
Intravenous access should be initiated with fluid resuscitation dictated by the provider’s assessment. Normal saline is recommended as the resuscitative fluid of choice, with the rate dictated by clinical judgment and adjusted as guided by electrolyte determination and clinical response. It cannot be overstated that in normothermic patients with confusion, EAH is the diagnosis of exclusion and aggressive fluid resuscitation should be withheld until electrolyte determination.
Once rectal temperature descends appropriately (~38.9°C), the cooling process should stop and the individual should be transported to a hospital for further observation20 and evaluation of possible sequelae, including rhabdomyolysis and renal injury, cardiac dysfunction and arrhythmia, severe electrolyte abnormalities, acute respiratory distress syndrome, lactic acidosis, and other forms of end-organ failure (Figure).
Figure.
Rapid cooling is more crucial than transport; transport poses a risk of delayed cooling, which can dramatically increase an individual’s risk of morbidity and mortality.20,23 In situations where a patient can be cooled on-site, physicians should pursue cooling before transporting the patient to a medical treatment facility.
Emergency Action Plan
Team physicians should be proactive in developing an emergency action plan to address possible EHS events. These plans should be site-specific, addressing procedures for all practice and home competition locations.12 All competition venues should have a CWI tub on-site in events where there is an increased risk of EHS.12,15,20 This tub should be set up and functional for all high-risk activities, including practices.12
Following recognition of a potential case of EHS, treatment teams should have procedures in place to transport athletes to the treatment area, obtain rectal temperature, initiate rapid cooling, and stabilize the athlete for transport to an emergency department (ED) for further evaluation.12,15 A written record of treatments and medications provided during athlete stabilization should be maintained and transported with the athlete to the ED.15 A list of helpful equipment and supplies for treatment of EHS can be found in Table 5.
Table 5.
EHS is a unique life-threatening situation where it is best to treat the patient on the sideline before transport.15 Those athletes transported before cooling risk spending an increased amount of time above critical temperatures for cell damage, which has been associated with increased morbidity and mortality. This mantra of “cool first, transport second” cannot be overemphasized, as those individuals with EHS who present to the ED with a persisting rectal temperature >41°F may risk up to an 80% mortality rate.24 Conversely, a recent large, retrospective study of 274 EHS events sustained during the Falmouth Road Race found a 100% survival rate when athletes were rapidly identified via rectal thermometry and treated with aggressive, rapid cooling through CWI.21