Ask a Doctor is a series of physician-authored columns offering insights and advice on common health topics. It is not a substitute for seeking medical care.
Few people expect to end up in the emergency department because of hot weather, but heat-related illness sends many people to the hospital every year.
During the summer months, I frequently see patients suffering from heat exhaustion and dehydration. Many who come in are surprised at how quickly their symptoms develop after feeling well spending time outdoors for hours. In more serious cases, patients arrive dangerously close to heat stroke– a life-threatening condition requiring immediate medical attention.
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According to data from the Canadian Hospitals Injury Reporting and Prevention Program, extreme heat events are contributing to a rise in emergency visits, particularly among vulnerable populations. And the Canadian Medical Association has said: “Illness from extreme heat waves places extra demands on a system already strained by a lack of primary care access and record ER wait times.”
As temperatures rise this summer, here are some things to know about heat-related illness and how to lower your risk.
Heat stroke is more than just ‘overheating’
Heat-related illness happens when the body can’t regulate its temperature properly. Although mild overheating might seem like no big deal, progression of this overheating, while failing to cool down, can lead to serious health complications.
The term heat stroke is often misused to describe much milder heat-related illness. If you’ve ever overheated or felt drained after a hot day, this is almost certainly not heat stroke. True heat stroke is a medical emergency characterized by confusion, loss of consciousness and a dangerously high body temperature. It requires emergency department care and rapid treatment; failing to recognize it can be fatal.
Environment Canada issues heat warning for Southern and Eastern Ontario
How to spot the warning signs
Heat-related illness exists on a spectrum, so recognizing early symptoms is key to avoiding progression:
- Heat rash: A red, raised rash in areas of sweat production (armpits, elbow creases, knee creases, and neck) that typically occurs several hours after heat exposure. The rash is usually itchy and takes a few days to resolve.
- Heat cramps: Painful muscle spasms, usually in the legs or abdomen. Heat cramps can occur during exertion in hot conditions due to a disproportionate loss of electrolytes compared to water (in sweat). They are easily treated with hydration, electrolytes and rest.
- Fainting: Heat can cause the blood vessels in the body to dilate and decrease blood pressure. This drop in blood pressure can lead to fainting episodes (or heat syncope) that are managed with hydration, electrolytes and removal from heat.
- Heat exhaustion: This consists of heavy sweating, dizziness, nausea/vomiting, headache and a fast heartbeat. It often occurs with prolonged or vigorous exertion in hot conditions. Without intervention, this can escalate to heat stroke. If any of these symptoms occur, it’s important to immediately get to a cool environment, and replace fluids and electrolytes. If symptoms don’t improve rapidly, this means progression to heat stroke is likely and the patient needs to go to the hospital emergency department immediately.
- Heat stroke: This is a medical emergency that is the progression of heat exhaustion. It consists of severe confusion, loss of consciousness or even seizures. The skin is typically hot and dry (with no sweating). This is a true medical emergency: Call 911 immediately.
When to seek medical care
While mild symptoms can often be managed with cooling strategies, some situations require urgent medical care:
- Dizziness, nausea or weakness that persists after rest and hydration.
- Any signs of heat stroke as outlined above.
- Individuals with underlying conditions such as heart disease, high blood pressure, diabetes and kidney disease who have prolonged symptoms of heat illness.
Who is most at risk?
Some groups are more vulnerable to heat-related illness due to their body’s inability to regulate temperature effectively or other factors such as socio-economic conditions. These include:
- Older adults: Aging affects the body’s ability to cool down efficiently.
- Infants and young children: Kids lose body fluids more quickly and may not be able to express discomfort from the heat clearly.
- People with chronic medical conditions: Underlying health conditions such as heart disease, diabetes or respiratory illnesses make temperature regulation more challenging.
- Outdoor workers and athletes: Exposure to extreme temperatures for long periods without adequate hydration or cooling breaks leads to increased risk.
- Certain medications: Medications such as diuretics, beta-blockers and antihistamines can impair heat tolerance.
- Unstably housed: Lack of access to air-conditioned spaces and exposure to extreme heat can increase risk.
Prevent heat illness by staying cool and monitoring for symptoms
The most important factors in avoiding heat illness start with awareness, preparation and recognizing symptoms early to help keep yourself and your loved ones safe.
- Hydrate, hydrate, hydrate: Drink plenty of water and don’t wait until you’re thirsty. Electrolyte-rich drinks (such as Pedialyte, Skratch Labs drink mix, low-sugar Gatorade or Powerade, or equivalent drinks) can help replace lost salt in sweat during extreme heat or exertion in the heat. Avoid caffeine (including energy drinks) and alcohol as much as possible, since both can lead to dehydration.
- Dress appropriately: Lightweight, light-coloured and loose clothing helps your body regulate heat better. Hats and sunglasses also provide protection.
- Limit time outside during peak hours and stay cool: The hottest hours (10 a.m. to 4 p.m.) are when heat exposure is most dangerous. Limit outdoor activities, especially exertion and exercise outdoors, during this time. When you are outside, take regular breaks indoors (ideally in air-conditioned spaces) or in the shade if you can’t get indoors. While outside, consider cool misting and cool compresses to help decrease body temperature.
- Pay attention to symptoms: Feeling lightheaded or nauseous? Stop what you’re doing, move to a cool place and rehydrate. Ignoring the early symptoms of heat exhaustion can quickly turn dangerous.
Dr. Shazma Mithani is an emergency physician working with adult and pediatric patients in Edmonton. Dr. Mithani is actively involved with the Canadian Medical Association, Alberta Medical Association and Sexual Assault Centre of Edmonton. She is also co-host ofThe Doc Talk Podcast.
Are you worried about heat in Ontario schools?
Ontario is expecting a heat wave starting this weekend, and we want to hear from teachers, families, and childcare providers about how you’re preparing to manage during this time.
What are the conditions like in your or your children’s classrooms? Do you have concerns about teaching or sending your child to school? And what do you think schools should do as climate change makes these extreme temperatures more frequent? Share your thoughts in the form below or send us an e-mail at [email protected] with “Heat in Schools” in the subject line.
