Ty Johnston, PharmD Student
Three months from now, you’ll look out your window and see nothing but white. Snow on the left, snow on the right, snow on your walkway, but your mind will be on a beach in Mexico. It seems that we work all winter to enjoy the perks of summer, and now that it’s here, let’s make the most of it; whether that be hiking, running, tennis, or whatever your forte may be. That said, outdoor activities do have risks, especially heatstroke during the hot summer months. Although typically minor, the severity of heat-related illnesses can range in severity, from a rash to potentially fatal heat stroke. Without timely medical attention, 80% of heat stroke cases can actually be life-threatening. However, timely treatment can reduce that rate to 10%.1 The people most at risk of heat-related illnesses are children and the elderly, however, anyone can potentially be affected by heat stroke, and it’s important to know the signs and be alert during a heat wave. In the end, the primary goal is prevention.
Although the different forms and severities of heat-related illnesses present with a wide range of symptoms, all of them result from an imbalance of heat. This could be from an excess of heat generated or absorbed by the body, or by an inability of the body to cool it’s temperature.
Here are some of the more common heat-related illnesses, listed in order of increasing severity:
- Heat rash: A rash that develops due to plugging of your sweat glands during chronic exposure to warmth.
- Heat cramps: These cramps usually occur in the lower body when your core body temperature has cooled back to normal. It may be due to the loss of salt and water from sweating. Heat cramps are most common in athletes who overexert themselves during training.
- Heat syncope: Syncope is a temporary loss of consciousness (or “passing out”) that occurs due to lack of blood supply to the brain. Syncope can have many different causes, but heat syncope occurs during heat exposure and people often return back to normal quickly.
- Heat exhaustion: Ranges from mild to moderate severity due to loss of electrolytes and water during heat exposure.
- Heat stroke: When your core body temperature is ≥ 40°C and your organs and nervous system begin to fail. Heat stroke is a life-threatening illness, and there are two types:
- Classic heat stroke: hyperthermia (increase in core body temperature) resulting from an impaired ability of your body to shed heat, or being in a persistently hot environment. Classic heat stroke usually takes days to develop.
- Exertional: hyperthermia that results from physical activity and heat exposure. Exertional heat stroke usually develops faster than classic.
Heat exhaustion and heat stroke are the two most important heat-related illnesses to be aware of, due to their potential to be life-threatening. It’s crucial that you seek medical treatment immediately once these warning signs of heat stroke are recognized.
- The symptoms of heat stroke include:
- Red, hot, and dry skin
- High core body temperature (>40oC), which is best detected by a rectal thermometer
- Heat exhaustion can lead to heat stroke if untreated, and it’s important to recognize warning signs such as:
- Nausea, vomiting, or both
- Muscle weakness or cramps
Self-treatment tips can help overcome mild heat-related illnesses, but it’s extremely important that once you see signs of heat stroke, you seek immediate medical treatment.
- Heat exhaustion: If these warning signs are recognized, then outdoor activity should be stopped immediately and the individual should rest in a cool, shaded area, and rehydrate. Recovery typically takes 2-3 hours, but if symptoms worsen or don’t resolve, then medical treatment should sought out as soon as possible.
- Strategies that can be applied to all mild heat-related illnesses:
- Stop activity and seek a cool, shaded and less humid environment.
- Drink plenty of fluid (see prevention).
- Consider a sports drink or oral rehydration solution (available at most pharmacies) to replenish your body’s cells with electrolytes, glucose and water. However, because sports drinks contain sodium and glucose, patients with diabetes, high blood pressure, heart failure, kidney problems, or fluid restrictions should avoid sports drinks unless there’s a sugar-free option available.
- Specific recommendations for mild illnesses:
- Heat rash: Keep the area dry.
- Heat cramps: Have a sports drink or an oral rehydration solution (as above). If the cramps don’t resolve in 1 hour or symptoms become severe, then you should seek advice from a healthcare professional.
- Heat syncope: Make sure the individual gets up slowly before seeking a cool and shaded environment.
What Factors Increase Your Risk?2
- Young children or elderly
- Physical activity in hot or humid environments
- Lack of airflow (ventilation or air-conditioning)
- Diseases such as obesity or hyperthyroidism; psychiatric, lung, kidney or heart diseases
- Medications that either increase your body temperature or cause water or electrolyte imbalances, such as antidepressants, antihistamines, antipsychotics, or diuretics (talk to a healthcare professional for more information)
- Environments with a lot of concrete or pavement
How to Prevent Heat-Related Illness2
Although medical treatment is available, heat stroke can still be fatal despite treatment. Prevention is the best strategy for managing heat-related illnesses. Here are some tips that you can use for yourself and the individuals that you have identified to be at increased risk.
- Try to stay in the shade.
- Wear loose-fitting and light-coloured clothing.
- Avoid strenuous outdoor activities when the sun is hottest (between 10am and 3pm) and when it’s humid outside. If this is not possible, take frequent breaks from your activity (10-20 minutes per hour of activity) in shade or an air-conditioned environment.
- Environment Canada has a chart, called a Humidex table, which individuals can use to determine the risk of heat-stroke based on the temperature and level of humidity.4 Here’s a link to the table: https://www.canada.ca/en/environment-climate-change/services/seasonal-weather-hazards/spring-summer.html#heat_and_humidity
- Drink plenty of fluids before, during and after any outdoor activity. Fluid intake should be increased, even without feeling thirsty. It’s recommended to drink approximately 0.5-1L of water during each hour of intense exercise. Also, limit the number of drinks that can make you dehydrated, such as coffee, tea, pop, and alcohol.
The Bottom Line
Some heat-related illnesses can be fatal. All individuals should be aware of the illnesses and the common warning signs so that they can protect themselves and individuals that may be at higher risk.
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- RxTx: CTMA. Heat-related Disorders
- RxTx: CTMA-i. Heat-related Illness
- Dynamed Plus: Heat-related Illnesses