In the not too distant past there was a frequent TV commercial which showed an egg cooking in a frying pan claiming this is what happens to your brain when you take drugs. It is a very scary demonstration of heat congealing protein. While not necessarily an accurate demonstration of what drugs do to a brain, it does show what heat can do to the living body.
Scientists have been studying the problem of temperature for decades and have learned a great deal about how the body regulates its temperature. The machinery of life operates in a very narrow range. It can’t be too cold and it can’t be too hot. It has to be just right.
We know that there is more than just the temperature on the thermometer. We know that high temperature linked with high humidity quickly reaches an upper limit of safety beyond which the human body can no longer cool itself by evaporating sweat on the surface to cool the body’s core.
A recent study by W. Larry Kenney et all at Penn State University had healthy young people swallow a small thermometer, sit in an environmental chamber and move only enough to mimic minimal daily activity. They found the critical upper environmental limit to be 88 F degrees at 100% humidity or 100 F degrees at 60% humidity. The dangers in hot dry environments is simply that the amount of sweat a body can produce is limited.
Children’s bodies have more trouble regulating body temperature as they have less skin surface to make cooling sweat compounded with their increased movement. Also children do not recognize they need to drink more water. When a person is thirsty they are already dehydrated.
The human body’s response to increasing core temperature is to try to push the hot blood to the surface to cool. This causes increase stress on the heart and other body systems. Many metabolic systems that assist in the energy that make the body’s organs work may shut down when the upper limits of heat is reached. This results in what is called heat stroke and result in severe neurologic damage (congealed protein) and death.
This heat stress is especially important when considering children, people with chronic conditions and those over the age of 65. All humans with heart disease, respiratory problems or other health problems are at higher risk. People over the age of 65 comprise 80-90% of heat wave causalities.
Some medications can increase the risk for a heat related illness including ibuprofen and diphenhydramine (Benadryl). Some can affect the body’s ability to regulate temperature, alter the blood flow to the skin or increase dehydration (diuretics). Some classes of drugs that can increase sensitivity to drugs are antidepressants, antipsychotics, high blood pressure meds, and lithium. It is important to read all the information about medications or speak to your pharmacist.
Stay out of the noon-day sun, drink lots of non-alcoholic liquids, and find a cool spot. Remember your children and pets.
Sally Robinson MD
Keeping Kids Healthy July 2023