As the temperature and humidity outside rise, what happens inside the human body can become a life-or-death battle, decided by just a few degrees.
Outdoor critical hazard point for illness and death from relentless heat several degrees lower than experts once thought, say researchers who put people in hot boxes to see what happens to them.
With most United States, Mexico, India And Middle East suffering from scorching heat waves, exacerbated by anthropogenic climate changeSeveral doctors, physiologists and other experts explained to The Associated Press what happens to the human body in such heat.
Core body temperature
The core body temperature at rest is usually around 98.6 degrees Fahrenheit (37 degrees Celsius).
That’s just 7 degrees (4 Celsius) away from heatstroke disaster, says Ollie Jay, professor of heat and health at the University of Sydney in Australia, where he directs the thermoergonomics laboratory.
Dr. Neil Gandhi, director of emergency medicine at Houston Methodist Hospital, said that during heat waves, anyone who comes in with a temperature of 102 or higher and does not have an obvious source of infection will be assessed for heat exhaustion or more severe heat stroke.
“During some heat waves, we will typically see body temperatures above 104 to 105 degrees,” Gandhi said. Another degree or three – and such a patient has a high risk of death, he said.
How the heat kills
According to Jay, heat kills in three main ways. Usually the first suspect is heatstroke—a critical increase in body temperature that leads to organ failure.
According to Jay, when the body’s core temperature gets too high, the body redirects blood flow to the skin to cool itself. But this diverts blood and oxygen from the stomach and intestines and can cause toxins normally found in the intestinal area to enter the circulation.
“It causes a cascade of effects,” Jay said. “Blood clotting throughout the body, multiple organ failure and ultimately death.”
But the biggest killer of heat is the stress it puts on the heart, especially in people with cardiovascular disease, Jay said.
This again begins with blood flowing to the skin to help remove internal heat. This leads to a decrease in blood pressure. The heart reacts by trying to pump more blood to keep you from passing out.
“It takes a lot more work out of your heart than usual,” Jay said. For someone with heart disease, “it’s like running after a bus with a dodgy hamstring.” It will give something.”
The third main path is dangerous dehydration. When people sweat, they lose fluid to such an extent that it can put serious strain on the kidneys, Jay says.
Many people may not be aware of their danger, said Gundy of Houston.
Dehydration can progress to shock, causing organs to shut down due to lack of blood, oxygen and nutrients, leading to seizures and death, said Dr. Rene Salas, a professor of public health at Harvard University and an emergency room physician at Massachusetts General Hospital.
“Dehydration can be very dangerous and even fatal for anyone if it becomes severe enough, but it is especially dangerous for people with medical conditions and those taking certain medications,” Salas said.
Dehydration also reduces blood flow and worsens heart problems, Jay said.
Attack on the brain
Heat also affects the brain. It can cause confusion or trouble thinking in a person, several doctors say.
“One of the first symptoms when you have a heat problem is if you’re confused,” said University of Washington public health and climate change professor Chris Eby. It won’t help much as a symptom, she says, because a person suffering from heat is unlikely to recognize it. And this becomes an even bigger problem as people age.
One of the classic definitions of heatstroke is a body temperature of 104 degrees, “in combination with cognitive dysfunction,” said Pennsylvania State University physiology professor W. Larry Kenny.
Humidity matters
Some scientists use a complex measurement of external temperature called wet-bulb temperature, which takes into account humidity, solar radiation and wind. It used to be that a wet-bulb temperature of 95 degrees Fahrenheit (35 Celsius) was when the body started to have problems, says Kenny, who also runs a hot cabinet lab and has conducted about 600 tests with volunteers.
His tests show the wet-bulb danger point is approaching 87 (30.5 Celsius). According to him, this figure began to appear in the Middle East.
And this is only for young healthy people. For older people, the danger point is a wet-bulb temperature of 82 (28 degrees Celsius), he said.
“Wet heat waves kill far more people than dry heat waves,” Kenney said.
When Kenny tested young and older adults in dry heat, the young volunteers were able to function in temperatures up to 125.6 degrees (52 degrees Celsius), while the older adults had to stop at 109.4 (43 degrees Celsius). According to him, with high or moderate humidity, people could not function even at such high temperatures.
“Humidity affects the ability of sweat to evaporate,” Jay said.
We are in a hurry to make our patients cool
Heatstroke is an emergency and medical workers try to cool the victim within 30 minutes, Salas said.
Best way: cold water immersion. Essentially, “you throw them in a bucket of water,” Salas said.
But they are not always nearby. So in emergency rooms, patients are given cool fluids intravenously, sprayed with nebulizers, ice packs placed in their armpits and groin, and placed on a cooling mat with cold water running inside.
Sometimes it doesn’t work.
“We call it the silent killer because it’s not as visually dramatic,” Jay said. “It’s insidious. It’s hidden.”