Extreme heat puts your heart and other organs at risk

Heat can be deadly, as this sign in Death Valley National Park
warns. (Photo by David McNew, Getty Images via NPR)

Extreme heat is the most deadly kind of weather for humans, and the body's main cooling mechanism, sweat, is not enough for extreme temperatures and humidity, so people risk organ failure, heart attack and kidney failure, reports Maria Godoy of NPR.

Organ failure can sneak up on you. "When your body is exposed to heat, it will try to cool itself down by redirecting more blood to the skin, says Ollie Jay, a professor of heat and health at the University of Sydney, where he directs the Heat and Health Research Incubator," Godoy notes. "But that means less blood and less oxygen are going to your gut. If these conditions go on long enough, your gut can become more permeable. Jay told her: "So, nasty things like endotoxins that usually reside and stay inside the gut start leaking out of the gut, entering the circulation. And that sets off a cascade of effects that ultimately result in death."

When the body redirects blood to the skin, the heart has to pump faster, "which can make you feel lightheaded – to keep your blood pressure up," Godoy explains. But not all hearts can manage a sudden or sustained jump in pace. "Those spikes in the heart rate can be triggers for a heart attack, Jay says, especially for the elderly and those with underlying heart conditions."

Sweat can only do so much, and comes with its own limitation: hydration, Godoy notes. "People can sweat as much as a liter and half per hour, Jay says. And if you don't replenish those fluids, you get dehydrated and your blood volume shrinks, which makes it harder to maintain blood pressure. That can strain your heart and your kidneys," and people with kidney disorders can be at greater risk.

Signs of mild heat exhaustion include headaches, dizziness, lethargy, and feeling unwell in general, Godoy notes: "If that happens, Jay says, get out of the heat and into the shade or indoors ASAP. Drink plenty of water and wet your clothes and skin. Immersing your feet in cold water can also help. . . . Jay says the goal is to cool down so you don't progress to severe heat exhaustion, where you might start vomiting or seem to lose coordination – signs of neurological disturbance. If your core body temperature rises to about 104 degrees Fahrenheit, Jay says, that's where you risk heatstroke."