Primary prevention

Prevention methods are very effective in limiting mortality and morbidity associated with heat stroke.[13] Vulnerable populations should be counseled to maintain adequate hydration, avoid heat exposure, wear loose, light clothing, and monitor their exertion level. Athletes should be advised to acclimatize for at least 3 to 4 days before exercising in the heat. Because a heat injury releases an inflammatory cascade that may increase risk on subsequent days, patients should minimize heat exposure for 24 to 48 hours after a mild injury.

Community-based measures

  • Physicians and other public health officials must take steps to educate their patients, especially those who have poor access to air conditioning or where there are cognitive obstacles to self-care. Most of the people in the US who experience heat stroke are older inner-city residents. Demographic studies have identified risk factors for death, including pre-existing medical conditions such as heart disease, pulmonary disease, or mental illness. In a case-control study of deaths in a Chicago heat wave, social isolation was the most important risk factor.[14] Even patients who had regular contact with home-health agencies were at increased risk. Critical protective factors included access to air conditioning.

  • Recommendations and programs to protect vulnerable populations from heat may be inadequate. For example, while many cities give fans to at-risk populations to prevent heat deaths, they are inadequate at extremes of heat and humidity, as the absence of a temperature/humidity gradient under extreme conditions impedes evaporative and convective cooling.[14] Although physicians routinely advocate adequate fluid consumption, most at-risk patients have significant cognitive or pharmacologic obstacles to achieving a positive fluid balance. As such, it has been proposed that community-based heat shelters be set up, and that visiting nurses actively recruit vulnerable patients to fill the shelters during dangerously warm periods.[15] Community centers, museums, and places of worship could also act as heat refuges.

  • Disseminating information about the dangers of heat is also crucial. Early warning systems using radio broadcasts and local newspapers have reduced heat-related deaths in US cities.[16]

Secondary prevention

Patients with a history of heat stroke may be more likely to have heat stroke again. Heat stress testing can aid in quantifying risk.[48] Adults with heat stroke should defer all physical exertion until performing a heat tolerance test, with recommendations based on the results of the test.[48] This approach is most helpful in young patients after an episode of exertional heat stroke.

Heat tolerance testing is part of the Israeli Defense Force protocol for managing and preventing heat stroke and may be useful in evaluating patients at risk of further episodes. Patients are subjected to the following protocols:

  • Heat tolerance is tested for 2 hours under heat-load conditions (104°F [40°C], 40% relative humidity).

  • Patient walks on a treadmill at 5 km/h (3 mph), 2% incline.

  • Rectal and skin temperatures, as well as heart rate, are monitored continuously.

  • Sweat rate is determined from weight loss while taking into account fluid intake and urine production.

Normal test results are defined as:

  • Rectal temperature not exceeding 100°F (38°C) after the first hour of the test.

  • Reaching rectal temperature plateau <101°F (<38.5°C) by the end of the second hour.

  • Reaching heart rate plateau <160 bpm during the test.

  • Sweat rate >500 mL/h after 2 hours.

When any condition is not met, the patient is suspected to be heat intolerant, and a second heat tolerance test is recommended for confirmation.

Elite athletes and soldiers may need to be tested with an enhanced protocol.[49] Up to 67% of women may be diagnosed as heat intolerant according to this protocol. Unique criteria may need to be developed for these patients.[50]

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