Heat Wave Health

Summer Health — Heat Illness

Dr. Zach

Summer 2018


Heat-related illness is a spectrum of disorders due to environmental exposure to heat. It includes minor conditions such as heat cramps, heat syncope, and heat exhaustion as well as the more severe condition known as heat stroke.


Your body normally cools itself by sweating. During hot weather, especially when it is very humid, sweating just isn’t enough to cool you off or doesn’t work because it’s too hot and humid to evaporate. Your body temperature can rise to dangerous levels and you can develop a heat illness.

Most heat illnesses happen when you stay out in the heat too long. When the humidity is high, sweat will not evaporate as quickly, preventing the body from releasing heat quickly.  Exercising and working outside in high heat can also lead to heat illness. Not being used to the heat is a risk factor for heat illness.  Older adults, young children, and those who are sick or overweight are most at risk. Taking certain medicines or drinking alcohol can also raise your risk.  Also dehydration, heart disease, mental illness, poor circulation, sunburn, drug and alcohol use.

Common medications can lead to health issues if taken when there is excessive heat. They include:

  • Medications taken to help sinus, allergy and cough and cold known as antihistamines and anticholinergic drugs. These medications can decrease the body’s ability to sweat and cool itself. Because the body is not cooling off as well as it should, risk of heat stroke is higher.
  • Antipsychotic medications affect a part of the brain that controls how the body manages heat to maintain a healthy body temperature. They can inhibit the body’s ability to regulate its temperature and can make heat stroke more likely.
  • Medications like beta-blockers and calcium channel blockers which can be taken to slow your heart beat and reduce blood pressure can slow the flow of blood to the skin. When this happens, the body has a harder time ridding the skin of heat.
  • Ephedrine, amphetamines and cocaine are stimulants that can increase metabolism and internal body temperature, as well as constrict blood vessels. They can make it harder for the body to release heat from the skin as well.


Heat-related illnesses include

  • Heat rash – skin irritation from excessive sweating. It is more common in young children.
  • Heat cramps – muscle pains or spasms that happen during heavy exercise. You usually get them in your abdomen, arms, or legs.  From loss of fluids, electrolytes like sodium.

Heat exhaustion is marked by muscle cramps, heavy perspiring, nausea, weakness, and dizziness or faintness.


If symptoms occur, stop what you’re doing, get out of the heat, and have a cool drink. Stretch or massage cramped muscles. If cooling off doesn’t resolve faintness, or if confusion, high fever, or seizures occur, seek emergency medical help.  If not treated, it can turn into heat stroke.


Heat stroke is a life-threatening emergency that can damage almost every major organ. Symptoms can include profound confusion and a gradual loss of consciousness or even coma, racing pulse, rapid breathing, and convulsions. Body temperature soars to 105°F/>40C or more. Call for emergency help immediately.


Official medical definition: Heat stroke is defined as a core body temperature usually in excess of 40ºC (104ºF) with associated central nervous system dysfunction in the setting of a large environmental heat load that cannot be dissipated


Commonsense precautions and an awareness of symptoms can help you prevent the illnesses–or get prompt treatment for them.


General advice:

Heat illnesses occur when the body’s own cooling mechanism becomes overloaded. Follow these tips to keep yourself safe:


Dress lightly in hot weather.  Light, breathable (cotton), loose clothing, light colour.

Limit physical exertion on extremely hot days.

Take frequent cooling-off breaks in the shade or air conditioning.

Drink plenty of liquids to prevent dehydration from perspiring, and to help keep your core temperature cool.

Be very cautious with caffeine and alcohol; they can cause your body to lose more fluid than you take in.

Stay informed. Listen to local news and weather channels or contact your local public health department during extreme heat conditions for health and safety updates.

During conditions of extreme heat, spend time in locations with air-conditioning such as shopping malls, and public libraries.

Many public pools will stay open late during heat wave.


https://www.cdc.gov/disasters/extremeheat/warning.html — table with summary of heat contitions and what to do


How long stay outside

How much to drink


To review, what are some of the signs that you are developing heat exhaustion?

Headache · Dizziness or fainting · Weakness · Wet skin · Irritability · Thirst · Nausea or vomiting · WARNING: If you feel FAINT, CONFUSED, or if you VOMIT – you need help FAST!


Signs of heat stroke?

May be confused · May be unable to think clearly · May pass out · May collapse · May have seizures (fits) · May stop sweating


Tips for Hydrating in Hot Weather

  • Start hydrating right away. It’s easier to maintain your fluid balance if you start out in a well-hydrated state.
  • Schedule regular beverage breaks and keep a water bottle handy so you can take frequent sips of water while you work or exercise.
  • Choose electrolyte-replacing drinks for maximum water absorption when you are exercising for more than an hour or when you are sweating excessively during exercise in hot weather.
  • Drink water after you’ve finished work or an exercise session.
  • Snack on fresh fruits that are rich in water, like berries, watermelon, peaches, and nectarines.
  • Don’t drink large amounts of plain water all at once—this can lead to ​hyponatremia or water-toxicity. This can also affect long-distance runners during races who push too many fluids. It is best to drink when thirsty during exercise and not push fluids.​​

One way to gauge your hydration level is to look at the color of your urine. If you’re well-hydrated, it should be pale. Also, you’ll be urinating more frequently.

Don’t wait to be thirsty





Experts are of the opinion that one should consume about .033 litres of water per kilogram one weighs. (per day)

The arithmetic for this goes simply like this.

If you weigh 75 kgs,

75 * .033 = 2.475 (litres of water you should ideally consume)

Experts are of the opinion that one should consume about .033 litres of water per kilogram one weighs.

One guideline is 4 cups or 8 cones of water per hour when working in the hot sun.

If you go out a lot during peak heat hours, where the temperature is more than 38 degrees Celsius, make sure you consume around 3-4 litres of water, at least. Your body needs that to rehydrate itself. Also, drink one glass of water per cup of coffee that you consume, in addition to your daily dose of water. The reason being that caffeine dehydrates you, that additional glass being used to replenish that loss.

You don’t just need to drink water in its purest form. Mix it up, have some lemonade or similar stuff. Avoid carbonated drinks as much as possible (and not just in summer). Eat fruits full of water, watermelon being a good example for this.

Treatment is rapid cooling, tx of complications, hydration, replacement of electrolytes.




It is important to know the signs and symptoms of heat exposure and how you should respond. Symptoms vary according to the type of heat-related illness. Babies and young children may show signs of restlessness or irritability and have fewer wet nappies. Older people may become lightheaded, confused, weak or faint.


Some heat-related illness and common symptoms include:

  • Deterioration in existing medical conditions – this is the most common health problem of heat stress.
  • Heat rash – sometimes called ‘prickly heat’, this is a skin irritation caused by excessive sweating. It can occur at any age, but is most common in young children. It looks like a red cluster of pimples or small blisters. It is most likely to occur on the neck and upper chest, in the groin, under the breasts and in the elbow creases.
  • Heat cramps – these include muscle pains or spasms, usually in the abdomen, arms or legs. They may occur after strenuous activity in a hot environment, when the body gets depleted of salt and water. They may also be a symptom of heat exhaustion.
  • Dizziness and fainting – heat-related dizziness and fainting results from reduced blood flow to the brain. Heat causes an increase in blood flow to the skin and pooling of blood in the legs, which can lead to a sudden drop in blood pressure. There can be a feeling of light-headedness before fainting occurs.
  • Heat exhaustion – this is a serious condition that can develop into heatstroke. It occurs when excessive sweating in a hot environment reduces the blood volume. Warning signs may include paleness and sweating, rapid heart rate, muscle cramps (usually in the abdomen, arms or legs), headache, nausea and vomiting, dizziness or fainting.
  • Heatstrokethis is a medical emergency and requires urgent attention. Heatstroke occurs when the core body temperature rises above 40.5 °C and the body’s internal systems start to shut down. Many organs in the body suffer damage and the body temperature must be reduced quickly. Most people will have profound central nervous system changes such as delirium, coma and seizures. The person may stagger, appear confused, have a fit or collapse and become unconscious. As well as effects on the nervous system, there can be liver, kidney, muscle and heart damage.

The symptoms of heatstroke may be the same as for heat exhaustion, but the skin may be dry with no sweating and the person’s mental condition worsens.


If you start to feel symptoms of heat exhaustion, move to a cool place, stop physical exertion, loosen clothes, put cool wet cloths on your body, or take a cool bath, take sips of water.  Fan yourself to use evaporation.

If throwing up, confused, symptoms don’t resolve, call 911.