Dear Dr. Eva,
I’m absolutely worn out with this hot weather we’ve been having – I just feel tired all the time. Is that what’s meant by “heat exhaustion?”
Dear Dr. Eva,
This week an old man sitting next to me at the bus stop fainted. I called 911. I thought maybe he had a heart attack. The paramedics came and said it was probably from the heat. Does that make sense? It was hot, but there was shade and he wasn’t sweating at all.
Dear BD and Sam,
I understand and relate to being tired of the heat, but that’s not what’s meant by heat exhaustion. Heat exhaustion is the milder form of heat related illness, with heat stroke being the severe form.
Heat-related illness begins when a person is exposed to more heat than the body can handle. The main way the body adjusts for heat is evaporative cooling – we sweat, and feel cooler as the sweat evaporates, carrying heat with it. So if a person does not sweat, they are likelier to get seriously ill.
The man Sam describes had “heat syncope,” fainting from the heat. This happens after the blood vessels open up wider to increase blood flow to the heat-stressed organs of the body. If too much blood is diverted from the brain, the person can faint. A milder effect of this blood vessel widening is the swelling of the hands and feet many people, especially women, develop in hot weather.
When the humidity is above 75 percent, as it has been on many recent days across the East Coast, sweat does not evaporate from the skin because the air is already holding the maximum possible amount of moisture. This is the truth behind the cliché; “It’s not the heat, it’s the humidity.”
When a person starts to feel sick in the heat, the important thing is not to ignore it. Get the person into an air conditioned place and encourage them to drink fluids. Since fans work by increasing the cooling evaporation of sweat from the body, if the weather is very humid or the person is not sweating, fans will not help cool a person down. People who do not sweat much are more likely to get heat illness.
Decreased sweating is common in older people, some women, and people taking certain medications. These medications include diuretics (“fluid pills”) and some mental health medications, especially medications for schizophrenia, which have a side effect of blocking the nerve signals that trigger sweating.
When heat illness progresses to the point that a person’s body temperature is high (like a fever), it is called heat exhaustion. Besides feeling tired, people with heat exhaustion may also have headache, nausea, dizziness, or mild confusion. In heat stroke, the confusion becomes severe and does not get better after 30 minutes in air conditioning and drinking fluids. At this point, the person should go to the hospital by 911 for IV fluids.
The commonest victims of heat stroke are elderly city residents who live alone without air conditioning. If you know someone who fits that description, please check on them and encourage them to go to a heat shelter or another air conditioned place during the hottest part of the day, 11:00 a.m. to 5:00 p.m.
To prevent heat illness, avoid being outside and especially avoid exercising when the temperature and humidity are both high. Dark clothing absorbs and concentrates heat, making you hotter. Even if you are a Goth biker, put away your black T-shirts and jeans and wear white or light colored clothing made of cotton or other materials that let air pass through. Keep drinking plenty of fluid – if you are at an outside event, have water in your hand all the time.
Remember that weather is bigger than we are and must be respected. The person who always jogs two miles a day regardless of the weather is asking for trouble. Alternatives include a treadmill in an air conditioned gym, jogging in the very early morning or late evening, or when the humidity is low.
So try and stay cool this Summer,
Ask Dr. Eva is distributed by Healthy Living News. Dr. Eva Hersh is Chief Medical Officer at Chase Brexton Health Services. Email comments and questions to [email protected] or write to Eva Hersh MD, Chase Brexton Health Services, 1001 Cathedral St., Baltimore, MD 21201