Recommendations

Key Recommendations

Heat exhaustion

Heat exhaustion, a milder form of heat illness, can present with nonspecific signs and symptoms. Treatment should focus on removing the patient from heat sources and augmenting intrinsic heat dispersal mechanisms.[18] This can include removing clothing, wetting the skin to aid in evaporative cooling, and ensuring that sweating is not compromised by volume depletion.[32] Mild volume depletion can be defined as <3% of total body weight.[23]​ Patients with mild volume depletion may experience symptoms and signs such as thirst or dry mucous membranes, although individual clinical findings are unreliable when taken in isolation.[24]​​

Hyponatremic heat exhaustion is a special case and should be ruled out before hydrating a heat-exhausted patient, as administration of hypotonic fluids such as water may worsen exercise-associated hyponatremia.[18][19]​ All patients showing signs of significant volume depletion (such as severe postural dizziness, postural hypotension or tachycardia) or hyponatremia, or who show significant central nervous system disturbance, should be transferred to a medical facility for further assessment and management. Core temperature and electrolyte balance should be monitored throughout treatment.

Heat stroke

Initial treatment of heat stroke in adults is aimed at rapidly decreasing core temperature.[33] This may be initiated in the field, for example, by external cooling, before definitive diagnosis is made. Clinical observations indicate that prognosis is closely linked to the amount of time a patient's temperature remains elevated. All patients should be assessed using Advanced Trauma Life Support (ATLS) protocols and managed as appropriate. If necessary, patients should receive resuscitation using the ABCs of acute care (securing airway, breathing, and circulation).[18][32]

Following transfer to a medical facility, cooling should be continued. Cooling methods may be either external or internal; external methods are preferred.[34][35]

When available, intravenous infusion of normal saline or Ringer lactate (Hartmann solution) should be given.[18] Infusions may require 1 to 1.5 L/hour. Antipyretics are not effective in treating heat stroke and should not be used.[18][31][32] Patients with severe exercise-associated hyponatremia may require boluses of hypertonic 3% saline.[19]

External cooling

External methods include immersion and evaporative cooling.[1][18][34][36]

Immersion cooling

  • Immersion in an ice bath or cooling blankets used in conjunction with ice packs may be the most rapid methods of cooling.[18][25][36][37] Ice packs should cover as much of the body as possible.[18][25]

  • Guidelines on exertional heat stroke recommend immediate cold water immersion (clothing/equipment removal is time consuming and should occur when the patient is in the tub).[25][38] There is evidence to suggest that acceptable cooling rates (>0.29°F/minute [>0.16°C/minute]) are possible in American footballers when immersed with their uniforms and pads on.[39]

  • Patients cooled in an ice bath frequently experience afterdrop (where their core temperature continues to decline even after they are removed from the bath). To prevent iatrogenic hypothermia, patients are typically removed from the ice bath once their core temperature reaches 100°F (37.8°C), though evidence suggests that cooling to 101.5°F (38.6°C) may be safer in preventing core afterdrop.[1][32][34][40] Therapeutic hypothermia with cooling to 91.4°F (33°C) has been reported but has not been studied widely.[41] Practitioners should be aware of falsely elevated rectal temperatures due to the insulating effects of body mass.[42]

  • Immersion may be a preferable technique when treating patients for whom exposure of the skin is culturally forbidden.

  • However, immersion can produce difficulties of access in case of a cardiac arrest, and bradycardia due to the diving reflex is not uncommon. In these cases, evaporative methods may be preferable.

Evaporative cooling

  • The patient's skin is exposed to warm air at 113°F (45°C) passing over the body while a mist of cool water at 59°F (15°C) speeds heat dissipation. Cooling rates with this technique have been measured at 0.5°F/minute (0.31°C/minute).[34]

  • Evaporative cooling may be preferred for older adult patients, or for those with compromised mental status, owing to the technical difficulties in performing resuscitation in an immersed patient.

Internal cooling

Internal cooling methods are effective in rapidly decreasing temperature.[43] Gastric, bladder, and rectal cold water lavage can be readily performed. Peritoneal and thoracic lavage with cold isotonic fluid may also be used, but are more invasive and so are used only in extreme cases. Invasive body-cavity lavage techniques have not been adequately studied so should not be considered first-line treatment for heat stroke.[18] Although rarely required, cardiopulmonary bypass or plasma exchange are also effective as a cooling method in this setting.[44] No data exist to help practitioners determine when internal cooling methods might be superior to external ones. As such, internal cooling methods should be regarded as an approach for use when external cooling may not be feasible or is ineffective.

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