How does heat kill? | Good Luck

The significant risk of illness and death from chronic heat is several degrees lower than experts once thought, say researchers who put people in hot boxes to see what happens to them.

As much of the United States, Mexico, India and the Middle East suffer from heat waves, exacerbated by human-caused climate change, several doctors, physiologists and other experts explained to the Associated Press what happens to the human body. when it’s hot.

Body temperature is the key

The body’s resting core temperature is usually 98.6 degrees Fahrenheit (37 degrees Celsius).

That’s only 7 degrees (4 Celsius) away from a disaster in the form of heatstroke, said Ollie Jay, a professor of heat and health at the University of Sydney in Australia, where he runs the thermoergonomics laboratory.

Dr. Neil Gandhi, director of emergency medicine at Houston Methodist Hospital, said during the heat wave anyone who comes in with a fever of 102 or higher and no clear source of infection will be considered for heat exhaustion or high fever.

“We’re going to generally see temperatures over 104, 105 degrees in some of the heat,” Gandhi said. Another degree or three and such a patient is at high risk of death, he said.

How heat kills

Heat kills in three important ways, says Jay. The first common suspect is heat stroke – a serious increase in body temperature that causes organ failure.

When the body’s internal temperature is too hot, the body directs blood flow to the skin to cool it down, Jay said. But that diverts blood and oxygen away from the stomach and intestines, and can allow toxins that are normally trapped in the intestinal tract to leak into the bloodstream.

“That opens up a lot of implications,” said Jay. “Whole body shutdown and multi-organ failure and, ultimately, death.”

But the biggest killer in heat is heart disease, especially in people with cardiovascular disease, says Jay.

It also starts with blood rushing to the skin to help remove heat from the body. That lowers blood pressure. The heart responds by trying to pump more blood to keep it out.

“You are asking the heart to do more work than usual,” said Jay. For someone with heart disease “it’s like running for a bus with a dodgy (muscle). We have something to offer.”

The third main way is dangerous dehydration. As people sweat, they lose fluid in a way that can put more strain on the kidneys, Jay said.

Many people may not be aware of their danger, said Gandhi from 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. Renee Salas, a professor of public health at Harvard University and an emergency room physician at Massachusetts General Hospital.

“Dehydration can be very dangerous and fatal for anyone if it gets bad enough — but it’s especially dangerous for those with medical conditions and certain medications,” Salas said.

Dehydration reduces blood flow and increases heart problems, says Jay.

Attacking the brain

Heat also affects the brain. It can cause a person to become confused, or have trouble thinking, several doctors say.

“One of the first signs that you’re in trouble with heat is that you’re confused,” said University of Washington public health and climate professor Kris Ebi. That is of little use as a sign because a person suffering from heatstroke is less likely to see it, he said. And it becomes a bigger problem as people get older.

One of the classic definitions of heat stroke is a core body temperature of 104 degrees “which is associated with cognitive dysfunction,” said Pennsylvania State University physiology professor W. Larry Kenney.

Moisture is important

Some scientists use a more complex external temperature measurement called the wet-globe temperature, which takes into account humidity, solar radiation and wind. In the past, it was thought that a wet bulb reading of 95 Fahrenheit (35 Celsius) was the point when the body started to have a problem, said Kenney, who also has a hot box lab and has conducted about 600 tests with volunteers.

His experiments show that the danger point of the wet bulb is close to 87 (30.5 Celsius). This is a number that has started to be seen in the Middle East, he said.

And that’s just for healthy young people. For older people, the danger zone is 82 degrees Celsius (28 degrees Celsius), he said.

“Humid heat waves kill more people than dry heat waves,” Kenney said.

When Kenney tested young and old people in dry heat, the young volunteers could work up to 125.6 degrees (52 degrees Celsius), while the adults had to stand at 109.4 (43 degrees Celsius). With high or moderate humidity, people couldn’t work at nearly as high a temperature, he said.

“Humidity affects the evaporation of sweat,” said Jay.

Rushing to make patients cool

Heatstroke is an emergency, and medical personnel try to revive the victim within 30 minutes, Salas said.

Best method: Immersion in cold water. Basically, “you throw them in a bucket of water,” Salas said.

But those aren’t always there. So emergency rooms pump patients with intravenous coolant, spray them with misters, put ice packs on their armpits and groin and place them on a cold mat with cold water running between them.

Sometimes it doesn’t work.

“We call it the silent killer because it’s not the kind of formal event,” said Jay. “It’s tricky. It is hidden.”