Disorders of heat extremes.


Abstract: As we get older we still aspire to doing the things our parents likely would, that may be sports, travel or just plain physical wok in the yard or garden. The body has an amazing thermostat mechanism, but we can still …

… manage to ignore or get caught out in living within it’s capabilities. This first post discusses heat related diseases and their prevention and management.

Heat stroke and dehydration

While temperature extremes usually affect older folks and younger children, adults can be caught out too. I remember a journey down to Montana when my wife contracted hypothermia on a white-water raft trip and again, it’s all easy to forget about the strength of the sun, especially in hazy conditions and when on a boat.

There is classic heatstroke (too much sun) and then there’s exertional heatstroke (working or exercising vigorously in the sun – running a marathon without adequate fluids to drink). I’m writing this at the beginning of the winter, but many will be travelling to warmer climes, so both extremes may be relevant today. – remember too that running marathons and such achievements are becoming more sought more as we live longer. In fact, heat stroke is becoming more common, not less, hence this post.

Heat stroke and heat exhaustion

Heatstroke, also known as sunstroke, is a condition caused by your body overheating (hyperthermia), usually because of prolonged exposure to, or physical exertion, in high temperatures. These serious forms of heat related illnesses are more common in the summer of course.

There is classic heatstroke (too much sun) and then there’s exertional heatstroke (working or exercising vigorously in the sun). There is  generally a lack of sweating in classic heatstroke, while sweating is generally present in exertional heatstroke.

Before a heat stroke occurs, people show signs of heat exhaustion such as dizziness, mental confusion, headaches, and weakness; if this occurs when the person is asleep, symptoms may be harder to notice of course.

Heat stroke occurs when the body’s ability to regulate heat (thermoregulation) is either not working well (as happens in age or disease – or alcohol), or is simply over whelmed  by a combination of excessive metabolic production of heat (exertion), excessive environmental heat (sun), and insufficient or impaired heat loss, (humidity or lack of sweat), resulting in an abnormally high body temperature.

Making things worse!

Substances that inhibit cooling and cause dehydration such as alcohol may change physiology and  predispose to so-called “classic” or non-exertional heat stroke (NEHS), both are potentially serious.

Exertional heat stroke (EHS) can happen in young people without health problems or medications – athletes, outdoor workers military workers or people who can’t come in from the sun and heat. First responders and police with heavy armor body amour .

In environments that are not only hot but also humid, it is important to recognize that humidity reduces the degree to which the body can cool itself by perspiration and evaporation and can accelerate the process. 


The risk of heat stroke can be reduced by observing precautions to avoid overheating and dehydration. Light, loose-fitting clothes will allow perspiration to evaporate and cool the body. Wide-brimmed hats in light colours help prevent the sun from warming the head and neck. Vents on a hat will help cool the head, as will sweatbands that have been have wetted with cool water.

Strenuous exercise should be avoided during hot weather, especially in the sun peak hours as well as avoiding glassed or confined space (such as cars) without adequate cooling, ventilation or air conditioning. A hat in the sun makes sense, especially one with vents!

Block out direct sun and other heat sources.

Drink fluids often, and before you are thirsty.

Wear lightweight, light-coloured, loose-fitting clothes.

Avoid beverages containing alcohol or caffeine.

Signs and symptoms

Heat Stroke –

Heat exposure for long periods, overloading ability to cool itself, very serious and potentially fatal

Body temperature higher than 40 C (104F)

Dry, hot skin

Rapid pulse and breathing

Confusion, seizures or loss of consciousness

Heat exhaustion – Exposure to heat without adequate fluid intake and inability to sweat adequately, less serious than Heat Stroke, but can lead to it.

Cool and clammy skin

Excessive perspiration

Rapid pulse


Nausea and or vomiting

Abdominal or limb cramps


In hot weather, people need to drink plenty of cool liquids and minerals such as salt which is also lost in sweating. Unfortunately just because you don’t feel thirsty doesn’t mean that you don’t need to take fluids in. What’s more, it’s not the more, the better, in fact there’s a serious and often poorly understood phenomenon, ‘water intoxication’.

Water intoxication: a possible complication during endurance exercise.

While a  better indicator is the colour of urine, that may not always help in a marathon.

Recognize the symptoms of heat-related illnesses, because heatstroke requires emergency treatment. Untreated heatstroke can quickly damage your brain, heart, kidneys and muscles. The damage worsens the longer treatment is delayed, increasing your risk of serious complications or death.



  1. Call 911
  2. Quickly move the victim to somewhere cooler
  3. Cool, wet cloths on the forehead and back of the neck
  4. Remove clothing that may be causing heat retention and replace with cool wet cloth/towel in their place. If possible, wrap in towel and splash soak in cold water
  5. Fan the victim


  1. Do not give them anything to eat or drink
  2. Do not use an alcohol rub

Heat exhaustion

  1. Move the victim to a cooler site
  2. If they are conscious, have him or her lie or sit down, elevate the feet, loosen any tight clothing.
  3. Never force anyone to drink but help them and if salt is available, that may help in small quantities too.

Dr Stephen Bray 2019

Leave a Reply

Your email address will not be published. Required fields are marked *