Doctors’ Notes: Increased heat stroke risk requires a strategy

*Republished from the Toronto Star's Doctors' Notes

This time of year, when many of us are eager to get out and enjoy some summer sun, hot humid weather can put us at risk of heat illness, such as heat stroke.

In my work as a sports medicine doctor, I would most commonly see heat illness in endurance sports, like marathons, and intensive outdoor training sessions, like in football. But, you don’t have to be a serious athlete to experience these conditions.

Usually, a healthy core body temperature is somewhere around 37 C. But if it climbs to 40 C internal organs — including your brain — may become damaged. When core temperature exceeds 40 C and there is any suggestion of neurologic abnormality, such as abnormal behavior or mood, heat stroke must be suspected.

Heat stroke is sometimes called a “heat attack” because it leads to complications, including death, if there is a delay in treatment. But, if you recognize and treat the signs early, including rapid cooling and quickly initiating contact with emergency response by calling 911, upward of 95 per cent will survive the “heat attack.”

There are two types of heat stroke. The first is classic heat stroke, which is related to being in an excessively hot environment. The severity of heat stroke is not always evident at first, as it can present with non-specific symptoms such as dizziness, nausea, and headache and may develop over days. Since sweating is one of the body’s ways of cooling itself, the inability to sweat in overwhelming heat, or anhidrosis, is a possible sign of this type of heat stroke.

Classic heat stroke tends to affect people at either end of the age spectrum — who are either very young or very old — because their bodies have less efficient core temperature regulation. Older adults who have chronic illnesses are at a particularly increased risk since some medications may predispose them to heat illness or limit their body’s natural ability to cool itself.

The second type is exertional heat stroke. Unlike classic heat stroke, this tends to affect younger people in good general health exercising in hot, humid environments, often wearing clothing or equipment that restricts cooling. Obesity can also make it more difficult to dissipate heat during physical activity. In these instances, the condition’s onset is relatively quick and may cause a person to collapse during physical activity.

Fortunately, there are some easy things you can do to keep safe on hot, muggy days:

• Limit exertion during peak heat. Try to schedule it during the cooler times of day like first thing in the morning or later in the evening. If peak heat exertion is unavoidable, try to reduce your intensity accordingly.
• Dress for the weather. If you can, choose breathable, lightweight fabrics that will help you keep your cool.
• Get lots of rest. If you’re going to be active for long periods of time in uncomfortably hot weather, a proper night’s rest is imperative.
• Stay hydrated. Make sure you get enough to drink, especially in high temperatures or humidity, or if you’re increasing your activity in these kinds of conditions. Use thirst as a guide for how much to drink, even in endurance events like marathons.
• Don’t overdo it. Keep the intensity of your exercise program in line with your general fitness level.
• Give yourself time to acclimatize. If you’re not used to the heat, allow time for your body to adjust. This is particularly true for people who might be moving to a new climate or travelling. For athletes, I usually recommend a period of a few weeks, but even five to seven days can help.

If you’re worried about heat stroke because someone is unresponsive and seems excessively hot, it’s a good idea to call 911 while you’re doing these things:

Help the person into a shady spot or into an air-conditioned building. Remove excessive clothing. You may consider applying ice packs to the affected person’s groin and armpits, spraying them with a garden hose or ice bath immersion. In short, anything you can do to lower their body temperature quickly can make a difference and may even be life-saving.

A person with heat stroke typically needs hospital monitoring and intervention. The initial goal is to rapidly lower the body temperature and close monitoring for organ damage. A doctor might recommend monitoring for hours to days, with regular temperature checks and investigations to evaluate and respond to signs of organ damage, such as to the kidney, liver, heart, and brain. Sometimes imaging, intravenous fluid resuscitation and medication are required. Return to exercise after exertional heat stroke should be guided by a medical doctor.

Summer is short, and many of us want to make the most of it. With some careful planning and a few modifications, you can play it safe and continue to enjoy your favourite activities.

Dr. Mark Leung is Program Director for the Enhanced Skills Program in Sport and Exercise Medicine in the Department of Family and Community Medicine at the University of Toronto. He is also a staff physician at the MacIntosh Sport Medicine Clinic and the Cleveland Clinic of Canada Midtown location.