What happens to our bodies when exposed to extreme heat? Doctors answer

Amid the effects of El Niño, PAGASA has been warning about the dangerous level of heat indexes in several areas of the Philippines.

Just this week, Dagupan City, Pangasinan and Sangley Point in Cavite experienced the highest heat index at 44°C and according to PAGASA it's bound to get worse all through May.

But you don't even need to see the temperature readings to know it is ridiculously and uncomfortably hot. Government offices and schools have even started reverting back to work-from-home setup to ensure the safety of employees and students amid the heat.    

Said PAGASA, heat index is the measure of temperature that a person feels, which is computed considering the actual air temperature and humidity.

In areas experiencing dangerous levels of heat index, PAGASA warned of heat cramps and heat exhaustion; it even warned of heat strokes in places of extreme danger level of heat index.

According to Doctor FX Apostol, primary care physician at the Medical City Clinic, these heat-related illnesses take place when a human body reaches a high temperature due to the extreme heat where one is in.

“Above 37.4°C, we consider a person as having a fever. Kapag naman umaabot na ng 40°C or hanggang 40.3°C — this is already a warning sign na ang isang pasyente ay puwede na magkaroon ng heat exhaustion na puwedeng mapunta sa heat stroke,” Apostol said. 

And should the body temperature continue at 40.3C for 10-15 minutes, “puwede na siyang magkaroon ng heat stroke.”

Dr. Geraldine Zamora-Abrahan, Associate Professor at the University of the Philippines College of Medicine, said cellular damage occur when our bodies reach a certain temperature.

Explains Dr. Amado A. Flores III, Chair of the Emergency Medicine Department of Makati Medical City, there are four compensatory mechanisms to help regulate our body's temperature.

First, there is an increase of sweat production, which "gives the body a chance to cool down and release heat." Then there is a decrease in heat production, so our metabolism slows down.  

Our blood vessels dilate to help bring down our core temperature, and finally, behavioral changes like reducing movements, wearing loose clothing and the like.  

"Once we can't compensate, these mechanisms will be deranged," Flores said, adding this happens  during prolonged heat exposure.  

Stages of heat illnesses

According to the doctors, our bodies first respond to extreme heat with thirst.

“‘Yung mga receptors natin, ang unang iti-trigger niyan is ma-pi-feel mo, nauuhaw ka," Apostol begins. "‘Yung mga regulators natin sa katawan, ‘yung mga receptors natin, sasabihin niya na ‘Uy, kailangan mo nang uminom. Kailangan mo nang mag-replenish'." 

Drink water upon feeling thirst, otherwise, "that would lead to dehydration" she said.

"High temperatures can lead to dehydration, lalo na kung increased ‘yung sweating mo,” Apostol continued.

Many things happens to the body when dehydrated. According to Manhattan Cardiology, "dehydration makes blood thicker," which makes it more difficult to pump. This raises your blood pressure, "para makalabas ang dugo," Flores said.  

While our bodies have the natural ability to reabsorb electrolytes like potassium back to our bodies, says Flores "dehydration makes it unable to reabsorb them." 

As such, it causes heat cramps, one of the first signs of a heat-related illness.

Heat cramps occur because the electrolytes that our muscles need are gone.

“‘Yung mga muscles natin, walang magamit na electrolytes — particularly sodium and potassium — dahil ‘yun ay lumalabas sa mga body fluids natin like ihi, sa pawis lalo na ‘pag mainit," Apostol said.

Remember the dilated blood vessels that help bring down our core temperature? “Lumalabas na ‘yung tubig doon sa mga blood vessels at pumupunta na siya sa extravascular area. ‘Yung tubig na dapat nasa ugat lang na umiikot, puwede na siyang lumipat din sa mga muscles, mga tissues, other parts of the body,” Apostol added.

Flores adds, "Nag-pu-pull kasi yung fluids pa baba, so nagkakaroon ng heat edema."

Said Zamora-Abrahan, severe muscle cramps often occur in the hands, calves, and feet, with lingering symptoms of soreness persisting for up to two days

If this not treated, the body will experience the second stage: heat exhaustion.

In this stage, Zamora-Abrahan explained “a person will additionally experience headache, low-grade fever, increased thirst and sweating, weakness, nausea, vomiting, dizziness, or even fainting. It is thought of as the body’s way to protect itself in times of overheating, or overexertion.”

According to Flores, there is also often an increase in heart rate. "Bumibilis ang paghinga, nag-ha-hyperventilate. Our bodies blow out carbon dioxide," he explained.  

This increased breathing causes potassium to go into the body, instead of it staying in the blood stream, which results in continued cramps.

While fatigue, dizziness and faintness are often associated with heat exhaustion, Flores says decreased levels of sodium can also cause either aggressive behavior or the opposite, passivity.

When still not given proper aid, the body will go to the third stage, which is heat stroke.

Zamora-Abrahan warns “Heat stroke is a medical emergency. It can be fatal."

"It occurs when the body is unable to cool down. Symptoms may include lack of sweat and very red and dry skin, and there is usually confusion and even seizures" he continued.

Heat stroke affects and may permanently damage our vital organs, including the heart, lungs, kidneys, liver, and brain.

Among those most at risk are the elderly, infants, those with chronic illnesses such as hyperthyroidism, and those taking certain medications, like diuretics.

"Early recognition and rapid cooling are essential — the more rapid the cooling, the lower the death rate from heat stroke,” Zamora-Abrahan said.

Can the human body adjust to temperature?

Every body senses heat differently due to differing metabolism, body shape, hydration status, sweating rate, and other hormonal conditions, like during pregnancy, Zamora-Abrahan said.

“May mga taong nato-tolerate nila dahil sanay sila sa maiinit na lugar. Nato-tolerate nila ‘yung mga extreme temperature nang mas matagal kaysa sa mga taong ‘di sanay sa maiinit na lugar kasi ‘yung perception ng katawan nila, hindi pa sila ganoon kasanay dun sa temperature na na-pi-feel natin na exposed madalas sa mainit na environment,” Apostol said.

According to Flores, it often takes one to two weeks for our bodies to acclimatize. Zamora-Abrahan however says acclimatization can also change over time, “with certain limits, of course.”

“It may take several weeks though, and happens when the body adjusts such as they are able to sweat more to dissipate body heat. For athletes, heat acclimatization is actually the best protection against heat-related illness and involves a gradual progression of duration and intensity of exercise over 10 to 14 days,” she said.

“‘Yan ang kagandahan sa katawan natin. Initially, ang katawan natin kapag na-expose siya sa extreme temperatures, there are regulations na nangyayari sa katawan natin para ma-adapt niya ‘yung certain extreme temperature bago magkaroon ng changes or damaging changes sa katawan,” Apostol explained.

As such, he said those who are constantly doing outdoor activities and workers who are usually exposed to heat are more affected.

“People who are exerting effort (like in sports or manual labor) use more of their muscles and heat is generated with energy expenditure, thereby making them more at risk for heat illnesses than those who do not. This does not mean we stop exercising or working though, but we should be mindful of preventive actions,” Zamora-Abrahan said.

What should we do to prevent experiencing these?

Staying hydrated is the first piece of advice from all the doctors.

“Kapag exposed ka nang mahabang oras sa extreme temperature, at least uminom ka ng 500 ml ng water every 20 minutes sa mga adult. Sa mga bata naman, nire-recommend nila at least one glass or at least 200 ml every 20 minutes,” Apostol said.

He added there’s no problem whether or not it is cold water as long as “hindi siya soft drinks, tea, iced tea, kasi mas mag-li-lead ['yon] sa dehydration." 

For Flores, "in extreme heat, it's important to include salt in drinks. Water is good but it can dilute the salts [in your body]. So things like sports drinks, are good because they can retain salt."

Zamora-Abrahan also reminded to “Clear with your doctor if you have been advised to limit fluids due to certain medical conditions.”

She also advised to avoid direct sun exposure, wear light-colored, lightweight, and loose-fitting clothing, take cool showers, use fans or air conditioning, and apply cold compresses to help lower your body temperature.

“Avoid intense physical exertion during the hottest parts of the day, and listen to your body's signals to rest when needed,” she said.

Meanwhile, Flores points to our food. "Less protein kasi mahirap siya to digest," he said, pointing to one of the mechanisms of the body — lowered metabolism.

"For summer, the recommendation is more carbohydrates," he said, adding avoid sugary drinks too because sugar is a diuretic. 

And finally, “Know the signs and symptoms of heat illnesses, check on vulnerable people, and if you see someone suffering from possible heat stroke, please bring the person to the hospital immediately.” 

— LA, GMA Integrated News