Stanford Medicine Newsletter Updates For the Local Community


Fending off heat stroke


Heat stroke can affect almost anyone when temperatures climb and the sunshine is intense. It can strike during a neighborhood softball game, at an outdoor concert, while sitting in a hot car or even when mowing the front lawn.

Stanford emergency medicine specialist Grant Lipman, MD, said three key elements contribute to heat illness: air temperature, the rate of sweat evaporation and radiant heat. Combine them with other factors, such as age, existing medical problems and level of exertion, and it’s possible to predict who is likely to suffer heat stroke, he said.

Physicians, sports enthusiasts and military officials use a special tool called a wet bulb globe temperature gauge, which uses three separate types of thermometers, to determine whether it’s safe to indulge in outdoor activities on hot days.  The rest of us need to be extra careful when the weather heats up.

Lipman cautioned that anyone planning a strenuous adventure in the heat prepare by acclimatizing in advance. “If you’re one of those audacious individuals planning to hike the Grand Canyon, then seven to eight days of repeated short amounts of exertion in that environment will help,” he said.

Grant Lipman


In general, staying safe in summer heat is fairly straightforward, he said, but it’s important to be aware of physical responses to avoid heat-related conditions. Here are some basics:

  • Humidity does matter. The more humid it is, the more difficult it is to sweat. Sweating—and having sweat evaporate by means of a fan (or natural breeze)—is one of the body’s most important means of cooling down its core temperature.
  • Slow down in hot weather. The more active you are, the more heat the body needs to dissipate. Your muscles use only a small portion of the energy you exert; the remainder is used to heat the blood and core temperature. Even walking can be too much if the outdoor temperature is too high to allow proper cooling.
  • Stay hydrated, but avoid liquids that are very cold. Drinks with alcohol and high amounts of sugar can backfire because they can trigger high loss of body fluid. Sports drinks can replace salt and minerals lost through sweating, but individuals on a low-salt diet should choose other options. Food should be cool and have limited spice.
  • Wear light-colored, lightweight and loose-fitting clothing and a wide-brimmed hat. Find shade when you can. When the heat is extreme, stay indoors in air conditioning or enjoy a cool bath or shower.
  • The risk of developing heat illness is higher among older adults and very young children and among people with fever, heart disease, high blood pressure, poor circulation and obesity. Those already nursing a sunburn are more vulnerable to heat. Certain medications, including antidepressants and diuretics, can also affect body temperature regulation.
  • Know the signs and symptoms of heat-related illnesses. For instance, if you’re not sweating and your skin feels hot, or if you feel nauseous, are dizzy or have a headache, slow down and take steps to cool the body. Mental confusion is another sign that the body is experiencing too much heat.
  • Act quickly to obtain first aid. Get out of the sun and stop moving. If possible, submerge yourself in a swimming pool, lake or body of water and move your limbs so the water circulates around your body. That’s the liquid version of wind, which will cool you faster.
  • If you would rather not stay inside, “Wake up extra early and get out before it’s too hot,” Lipman said. “Don’t do anything in the middle of the day.” 

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