As temperatures and humidity rise outside, what happens inside the human body can become a life-and-death battle decided by just a few degrees.
The critical danger point outside for illness and death due to incessant heat is several degrees lower than experts once thought, say researchers who put people in hot boxes to see what happens to them.
With a large part of UNITED STATES, Mexico, India and the Middle East suffering from scorching heat waves, worsened by human-caused climate changeSeveral doctors, physiologists and other experts explained to the Associated Press what happens to the human body in such heat.
Key body temperature
The resting core body temperature is usually around 98.6 degrees Fahrenheit (37 degrees Celsius).
That’s only 7 degrees (4 Celsius) of disaster in the form of heat stroke, said 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 The hospital said that during heat waves, anyone with a fever of 102 or higher and no clear source of infection will be evaluated for heat exhaustion or more serious heat stroke.
“We will regularly see core temperatures above 104, 105 degrees during some heat events,” Gandhi said. One or three more degrees and such a patient is at high risk of death, he said.
How heat kills
Heat kills in three main ways, Jay said. The usual first suspect is heat stroke – a critical increase in body temperature that causes organ failure.
When the body’s internal temperature becomes too hot, the body redirects blood flow to the skin to cool itself, Jay said. But this diverts blood and oxygen from the stomach and intestines and can allow toxins normally confined to the intestinal area to leak into the circulation.
“It sets off a cascade of effects,” Jay said. “Clotting around the body and multiple organ failure and, ultimately, death.”
But the biggest killer in heat is the strain on the heart, especially in people with cardiovascular disease, Jay said.
It starts again with blood rushing to the skin to help carry away core heat. This causes blood pressure to drop. The heart responds by trying to pump more blood to keep you from passing out.
“You’re asking the heart to do a lot more work than it usually has to do,” Jay said. For someone with heart disease, “it’s like running for a bus with questionable hamstrings.” Something is going to give.
The third main pathway is dangerous dehydration. When people sweat, they lose fluids to such an extent that it can seriously stress the kidneys, Jay said.
Many people may not realize the danger, said Gandhi of Houston.
Dehydration can progress to shock, causing organs to shut down due to a 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 physician at Massachusetts General Hospital.
“Dehydration can be very dangerous and even fatal for anyone if it gets severe enough, but it is especially dangerous for people with medical conditions and taking certain medications,” Salas said.
Dehydration also reduces blood flow and amplifies heart problems, Jay said.
Attack the brain
Heat also affects the brain. This can cause confusion or difficulty thinking, several doctors said.
“One of the first symptoms you experience with heat is confusion,” said Kris Ebi, a professor of public health and climate at the University of Washington. It’s not much help as a symptom because the person suffering from the heat is unlikely to recognize it, she said. And it becomes an even bigger problem as people get older.
One of the classic definitions of heat stroke is a core body temperature of 104 degrees “associated with cognitive dysfunction,” said W. Larry Kenney, a professor of physiology at Pennsylvania State University.
Humidity matters
Some scientists use a complex measurement of outdoor temperature called wet bulb temperature, which takes into account humidity, solar radiation and wind. In the past, it was thought that a humid temperature of 95 Fahrenheit (35 Celsius) was the point where the body started to have problems, said Kenney, who also runs a hot box lab and has performed nearly 600 tests with it. volunteers.
His tests show the wet bulb danger point is closer to 87 (30.5 Celsius). It’s a number that’s starting to show up in the Middle East, he said.
And it’s just for healthy young people. For seniors, the danger point is a humid temperature of 82 (28 degrees Celsius), he said.
“Moist heat waves kill many more people than dry heat waves,” Kenney said.
When Kenney tested young and old people in dry heat, young volunteers could run up to 125.6 degrees (52 degrees Celsius), while older people had to stop at 109.4 (43 degrees Celsius ). With high or moderate humidity, people wouldn’t be able to function in such high temperatures, he said.
“Humidity impacts the ability of sweat to evaporate,” Jay said.
Rushing to make patients cool
Heatstroke is an emergency and medical personnel try to calm the victim within 30 minutes, Salas said.
The best solution: Immersion in cold water. Basically, “you drop them in a bucket of water,” Salas explained.
But these are not always there. So emergency rooms pump patients with cold fluids intravenously, spray them with foggers, put ice packs in their armpits and groin, and place them on a cooling mat with cold water running inside.
Sometimes it doesn’t work.
“We call it the silent killer because it’s not that kind of visually dramatic event,” Jay said. “It’s insidious. It’s hidden.
