Heat Related Injuries- How to recognize and treat the most common heat related injuries

Heat Related Injuries can end your chances of survival if you aren't aware of their causes.

Heat Related Injuries can end your chances of survival if you aren’t aware of their causes.

Even under “normal” circumstances heat related injuries can quickly become life threatening if not recognized quickly and treated appropriately. As paramedic in Texas I worked medical support for the Hotter Then Hell Hundred, a one hundred mile bike race through North Texas during the heat of August, and at every single race I worked I saw the effects of heat related injuries seasoned, in shape, professional bike racers.

We would treat multiple cases of heat cramps and heat exhaustion and at least one case of heat stroke each year and that was on people who had trained for that grueling race. As a contractor in Iraq, Afghanistan, and Africa I got to see even more heat injuries of varying degrees among well-trained people that became casualties of heat injury. Now imagine someone thrust into a survival or SHTF situation that is average shape having to deal with those stresses.

In this article we are going to look at how your body normally works to keep you cool, the signs and symptoms of various heat injuries, and how you can treat them in a survival/SHTF situation.

 A few words about heat.


Wet Bulb Globe Temperature (WBGT) is a composite temperature used to estimate the effect of temperature, humidity, wind speed (‘wind chill’), and visible and infrared radiation (e.g., sunlight) on humans. The WBGT index was developed in 1956 by the United States Marine Corps at Parris Island to reduce heat stress injuries in recruits. It is determined with special equipment and calculated to reflect components of air, humidity and wind that affect ‘actual temperature’ experienced by personnel: WBGT is derived from the formula: 0.7Tw + 0.2Tg + 0.1Td

Tw = Natural wet-bulb temperature (with dry-bulb temperature indicates humidity)

Tg = Globe thermometer temperature (also known as black globe thermometer)

Td = Dry-bulb temperature (actual air temperature)

Wet Bulb Globe Temperature (WBGT) Categories
Category WBGT, °F WBGT, °C Flag color
1 <= 79.9 <= 26.6 White
2 80-84.9 26.7-29.3 Green
3 85-87.9 29.4-31.0 Yellow
4 88-89.9 31.1-32.1 Red
5 => 90 => 32.2 Black
  • Add 5°F for rucksack or body armor


The categories in the WBGT index are used in the military as a guide that gives NCO’s and Officers a guide to Work-Rest cycles under different temperatures.

Work-Rest-Water Chart Courtesy of US Army Medical Command

Work-Rest-Water Chart Courtesy of US Army Medical Command

Heat Index Chart Courtesy of US Army Medical Command.

Heat Index Chart
Courtesy of US Army Medical Command.

A good way to keep track of how much water you are drinking is to make a Ogden Cord. A Ogden Cord can be as simple as a 6”-8” piece of 550 cord attached to a button that you tie a knot in every time you finish 1 quart of water or you can use a set of Ranger beads (Pace Count Beads) by pulling one of the beads down every time you finish a quart of water. Regardless of which method you use to keep track of how much water you are drinking it will help you make sure that you are drinking plenty of water based on the work-rest-water chart above.

Risk Factors for Heat Injury

There are a number of risk factors that can lead to heat injury. By knowing these risk factors you can mitigate those risks and help prevent heat injuries.

Environmental Factors:

  • Higher temperature
  • High humidity (WBGT)


  • High exertion
  • Heavy loads/gear
  • Repeated strenuous days

Lack of Acclimatization:

Acclimatization requires aerobic exercise in a warm environment. The body needs to adjust to environmental heat stressors prior to high exertion activities; simply being outside doing normal activities is not enough.

NOTE: Hot weather is a key risk factor for heat injuries, HOWEVER: Heat illnesses can occur under green flag temperature conditions due to previous days’ conditions and dehydration.

Individual Risk Factors:

  • Poor fitness
  • Being Overweight
  • Age > 40
  • Gender (female)
  • Minor illness
  • Medication: Antihistamines (e.g., Benadryl, Atarax, CTM), decongestants (e.g., Sudafed); high blood pressure (e.g., diuretics, beta blockers); psychiatric drugs (e.g., tricyclic antidepressants, antipsychotics).
  • Alcohol in the past 24 hours
  • Prior heat injury
  • Skin rash, sunburn, or poison ivy
  • Blood donation (< 3 days)
  • Sleep deprived
  • Highly motivated – the desire to get out of the survival/SHTF situation may lead some people to continue to push themselves as early signs/symptoms of heat injury occur. These people should not be discouraged from pushing themselves but you should be aware of their tendency so that they can be watched more closely.

How your body cools itself.

Your body normally cools itself by sweating, during hot weather, especially with high humidity, sweating just isn’t enough. If you are losing (sweating out) more fluid then you are taking in you will become dehydrated, raising your risk of heat injury. Eventually your body temperature can rise to dangerous levels and you will develop a heat injury.

Most heat injuries occur from staying out in the heat too long, exercising too much for your age and physical condition are also factors. Older adults, young children and those who are sick or overweight are most at risk. Drinking fluids to prevent dehydration, replenishing salt and minerals, and limiting time in the heat can help reduce your risk of heat injury.


Dehydration can be prevented simply by making sure you drink plenty of water. In a survival/SHTF situation you can be pretty sure you WILL become at least mildly dehydrated unless you are near or have a good supply of drinking water with you.

You need to keep this in mind because even mild cases of dehydration can significantly degrade your performance as noted below:

  • Losing 4% of body weight from dehydration degrades physical performance 50% or more!
  • This 4% body weight loss is possible in less than 2 hrs!
  • Increases core body temp
  • Every 1% loss of body weight increases core temp .10-.23°C or .18-.40°F (increasing risk of more serious heat illness)

The best solution to dehydration related problems is prevention!

Urine Color Chart to gauge dehydration level. Courtesy of US Army Medical Command.

Urine Color Chart to gauge dehydration level.
Courtesy of US Army Medical Command.


Of all heat injuries, Heat Cramps are the least severe and easiest to treat. Recognizing the signs and symptoms of heat cramps quickly will allow you to take the steps needed to prevent them from becoming something more serious.

The signs and symptoms of Heat Cramps are:

  • Severe cramping of limbs (usually legs)
  • Grasping or massaging a limb (arm or leg) or bending over in an effort to relieve the pain of an abdominal cramp.
  • Skin wet with perspiration.
  • Unusual thirst.

Treatment of heat cramps:

  • Move the casualty to a cool, shaded area to rest. Use poles, ponchos, blankets, or other available materials to improvise a shade, if needed.
  • Loosen the casualty’s clothing around his neck and waist and loosen his boots or shoes.
  • Have the casualty slowly drink one quart of cool water.
  • Keep the casualty calm and in a cool place drinking water (slowly) until cramps are gone.
  • If cramps persist, you need to find medical attention ASAP.

 Heat Exhaustion

Heat Exhaustion is a serious heat related injury that you need to recognize before it becomes a case of heat stroke.

The Signs and Symptoms of Heat Exhaustion:

  • Profuse sweating with pale, cool skin
  • Dizziness
  • Headache
  • Loss of appetite
  • Nausea
  • Weakness
  • Clumsy/unsteady walk
  • Muscle cramps
  • Nausea (with or without vomiting).
  • Chills (“goose-flesh”).
  • Rapid breathing.
  • Urge to defecate.
  • Tingling in hands or feet.
  • Mental confusion.

Treatment of Heat Exhaustion:

  • Move them to a cool shaded area to rest. Improvise a shade, if necessary.
  • Position them on their back with his legs elevated (shock position).
  • Remove the clothing around their neck and waist and loosen their boots or shoes.
  • Pour water over them and fan them to cool their body faster (misting of water workers best).
  • Have them slowly drink one quart of cool water.
  • If they cannot drink the water because of nausea or if they vomits, you will need to start a large-bore (14ga) IV of Normal Saline or Lactated Ringers and run wide open (only if you are trained to do so).
  • Once they recover, have them rest or perform only light duties for the rest of the day if the situation permits.

The key is to cool them as quickly as possible to prevent them from having a heat stroke.

 Heat Stroke

Heat Stroke is the most serious of the heat related injuries you could suffer. In heat stroke, the body’s internal (core) temperature increases to dangerous levels. If their body temperature is not lowered quickly, brain injury or death may result. Anyone who is not perspiring or perspiring very little while others who are performing the same work and perspiring freely is in danger of heat stroke. Take emergency measures immediately!

Signs and Symptoms of Heat Stroke:

  • Skin that is hot, dry, and red
  • Headache
  • Weakness
  • Dizziness
  • Mental confusion
  • Combative/Violent
  • Nausea or stomach pains
  • Seizures
  • Weak and rapid pulse and respiration
  • Sudden loss of consciousness

Treatment of Heat Stroke:

  • Move them to a cool, shaded area or improvise a shade
  • Loosen or remove their outer garments
  • Position them on their back with their feet raised while pouring cool water over them, fanning them vigorously, and massaging their arms and legs with cool water (Mist is more effective than pouring water)
  • Place instant Ice packs (if available) on either side of the neck, in both arm pits, and the groin
  • Have the casualty slowly drink one quart of cool water if he is able
  • If unable to drink, start bilateral (both arms) large-bore (14ga) IV’s of Normal Saline or Lactated Ringers and run wide open line (only if trained to do so)
  • Do not delay transport to a medical facility just to start cooling measures

You need to cool the person as quickly as possible, their brain and other vital organs are being damaged every second they stay over heated!

If you are in a survival/SHTF situation seeking medical attention may not be possible, so it is going to be up to you to get their core body temperature down and keep it that way!  As you cool them down look for signs of hypothermia (uncontrollable shivering, rapid respiration, etc.) if signs of hypothermia present you need to STOP cooling them and make sure they get warm. I know sounds counterproductive but you don’t want to trade one issue for another.

Once you have them cooled you need to make sure that they do nothing but rest for at least 36-48 hours and watch them for any signs they may be overheating (or becoming hypothermic) again. By resting it allows their body to get back to “normal.” During this “Rest Time” make sure they drink plenty of water or that you have an IV going to make sure they become hydrated again.

Hyponatremia-Low Blood Sodium (Water Intoxication)

Another heat related injury you may see is hyponatremia or “Water Intoxication. Quantitatively speaking, it means having a blood sodium concentration below 135 millimoles per liter, or about 0.4 ounces per gallon, the normal concentration lying somewhere between 135 and 145 millimoles per liter. Severe cases of hyponatremia can lead to water intoxication, an illness whose symptoms include headache, fatigue, nausea, vomiting, frequent urination and mental disorientation.

In humans the kidneys control the amount of water, salts and other solutes leaving the body by sieving blood through their millions of twisted tubules. When a person drinks too much water in a short period of time, the kidneys cannot flush it out fast enough and the blood becomes waterlogged. When I was in school to become a paramedic one thing that was drilled into our heads was, “Water follows salt.” Drinking too much water too quickly will cause water to be drawn to regions where the concentration of salt and other dissolved substances is higher, excess water leaves the blood and ultimately enters the cells, which swell like balloons to accommodate it.

Most cells have room to stretch because they are embedded in flexible tissues such as fat and muscle, but this is not the case for neurons. Brain cells are tightly packaged inside a rigid boney cage, your skull, and they have to share this space with blood and cerebrospinal fluid. Inside the skull there is almost zero room for the brain to expand and swell with this influx of water.

Thus, brain edema, or swelling, can be disastrous. Rapid and severe hyponatremia causes entry of water into brain cells leading to brain swelling, which manifests as seizures, coma, respiratory arrest, brain stem herniation and death.

At what point did people get the idea that guzzling enormous quantities of water is healthful? A few years ago Heinz Valtin, a kidney specialist from Dartmouth Medical School, decided to determine if the common advice to drink eight, eight-ounce glasses of water per day could hold up to scientific scrutiny.

After scouring the peer-reviewed literature, Valtin concluded that no scientific studies support the “eight x eight” dictum (for healthy adults living in temperate climates and doing mild exercise). In fact, drinking this much or more “could be harmful, both in precipitating potentially dangerous hyponatremia and exposure to pollutants, and also in making many people feel guilty for not drinking enough,” he wrote in his 2002 review for the American Journal of Physiology—Regulatory, Integrative and Comparative Physiology. And since he published his findings, Valtin has said, “Not a single scientific report published in a peer-reviewed publication has proven the contrary.”

Most cases of water intoxication do not result from simply drinking too much water. It is usually a combination of excessive fluid intake and increased secretion of vasopressin (also called antidiuretic hormone). Vasopressin is produced by the hypothalamus and secreted into the bloodstream by the posterior pituitary gland; vasopressin tells the kidneys to conserve water. Its secretion increases in periods of physical stress—in a survival/SHTF situation, for example—and may cause the body to conserve water even if a person is drinking excessive quantities.

Every hour, a healthy kidney at rest can excrete 800 to 1,000 millilitres, or 0.21 to 0.26 gallon, of water and therefore a person can drink water at a rate of 800 to 1,000 millilitres per hour without experiencing a net gain in water. If that same person is in a survival/SHTF situation, however, the stress of the situation will increase vasopressin levels, reducing the kidney’s ability to get rid of water to as low as 100 millilitres per hour. Drinking 800 to 1,000 millilitres of water per hour under these conditions can potentially lead a net gain in water, even with considerable sweating.

You should balance what you’re drinking with what you’re sweating, and that includes sports drinks, which can also cause hyponatremia when consumed in excess. If you’re sweating 500 millilitres per hour, that is what you should be drinking. Drinking more then you need can lead to serious consequences.

By paying attention to your environment, your water intake, and resting often on hot days you will greatly reduce your risk of suffering a heat related injury.

I look forward to seeing your comment and as always, Train to Survive!


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