Heat Illness: Dehydration, Heat Exhaustion or Heatstroke?

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Soaring temperatures can cause dehydration and serious heat-related illnesses such as heat exhaustion and heatstroke. Knowing how to spot and treat heat illness can help you stay safe when the heat’s on the rise. 

The Centers for Disease Control and Prevention reports that each year in the United States, heat-related illness leads to more than:

  • 67,000 hospital emergency room (ER) visits
  • 9,200 hospital admissions
  • 700 deaths

Keep reading to learn more about dehydration and the 2 most serious types of heat illness.

What Is Heat Illness?

Heat-related illness can happen when your body heats up too fast and can’t cool itself down effectively. Heat illness occurs along a continuum and ranges from mild to life-threatening.

It often starts with milder forms such as heat rash and heat cramps. But left untreated, heat illness can progress quickly to the most severe forms on the spectrum.

Who’s at Risk for Heat Illness?

Anyone who spends too much time in the heat can get heat illness, even if you’re young or in good health. But you may be more prone to them if you:

  • Are 4 years-old or younger
  • Are 65 years-old or older
  • Drink alcohol
  • Live in areas where the weather’s very hot or that have a lot more asphalt and concrete, which absorb more of the sun’s energy — this is called the “urban heat island effect”
  • Take medicines or have chronic health conditions that impair blood circulation (flow), as well as your ability to sweat or control body temperature — such as diabetes, heart disease, high blood pressure and obesity
  • Work or are active in hot climates, especially for lengthy periods of time

What Is Dehydration?

Dehydration isn’t a heat illness per se, but it can place you at higher risk for getting one. The condition occurs when your body doesn’t have enough fluids. 

Heat can cause you to sweat more or spike fevers. You then lose fluids more quickly.

Losing too much fluids can cause an imbalance in your body’s electrolytes. These are vital minerals your body needs to function. They include calcium, magnesium, potassium and sodium.

What Are the Symptoms of Dehydration?

Dehydration may cause you to feel:

  • Very hot or have chills
  • Very thirsty
  • Confused
  • Dizzy, faint or lightheaded
  • Tired

You may also have:

  • Cravings for sugar but little appetite
  • Dark urine
  • Dry mouth, tongue or cough
  • Dry or flushed skin
  • Fast pulse but low blood pressure
  • Headache
  • Muscle cramps

You may also urinate less often. This is because your kidneys hold on to urine when the amount of fluids in your blood gets too low.

Infants and young kids may appear listless, irritable or unusually sleepy or tired. They may also have a fever and:

  • Cheeks and eyes that appear sunken
  • Dry mouth and tongue
  • No tears when they cry
  • No wet diapers for 3 or more hours
  • Sunken top fontanelle (soft spot on baby’s skull)

How Is Dehydration Treated?

Drinking fluids such as water can help with mild cases of dehydration. You can also eat water-rich whole foods such as fruits and vegetables. 

Sports drinks with no added sugar can also help balance and replenish electrolytes but stay away from drinks with alcohol or caffeine, as these can dehydrate you further. Infants and young kids can have electrolyte drinks made for their age group and body weight, such as Pedialyte. 

If you have moderate to severe dehydration symptoms, you’ll need intravenous (IV) fluid replacement. Severe symptoms must be treated at the ER right away.

Talk with your doctor if you have kidney disease or heart failure. When you have these conditions, fluids can build up and wreak havoc in your body when you take in too much of it. Therefore, it’s best to follow your doctor’s guidance on how much and which types of fluids help you hydrate safely.

Heatstroke vs. Heat Exhaustion

The most severe forms of heat illness are heat exhaustion and heatstroke, with heatstroke being the most serious of them all.

What Is Heat Exhaustion?

Heat exhaustion (also called heat stress) happens when your body loses too much of its fluids and electrolytes, often due to excess sweating. Your body then overheats and can’t cool itself down effectively.

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What Are the Symptoms of Heat Exhaustion?

Symptoms of heat exhaustion include:

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  • Blurry vision
  • Fast, shallow breaths
  • Feeling weak or tired
  • Feeling faint, dizzy or lightheaded
  • Fever
  • Headache
  • Edema (swelling) in your ankles, feet or hands
  • Heavy sweating, which can cause clammy (cool and damp) skin
  • Muscle cramps
  • Nausea or vomiting
  • Orthostatic hypotension (low blood pressure with a fast but weak pulse when you stand up)
  • Thirst
  • Less urine

How Is Heat Exhaustion Treated?

You can treat mild heat exhaustion with first-aid cooling measures such as:

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  • Moving to and resting in a cool place such as an air-conditioned building or in front of a fan or shady area
  • Lying on your back and propping your legs above heart level to boost blood flow and lessen swelling in your limbs
  • Taking off extra layers of clothing and loosely wearing what you still have on
  • Placing ice packs, cold compresses or cool, damp towels against your armpits, groin, neck and torso
  • Soaking, spraying or dousing yourself with cool water
  • Taking frequent sips of cool healthy fluids 

If your mild heat exhaustion symptoms persist or get worse, get immediate medical care, especially if you’ve been trying cooling measures for around an hour already. Heat exhaustion can quickly progress to heatstroke.

What Is Heatstroke?

Heatstroke is a life-threatening health emergency that requires prompt medical care. If not treated quickly, this heat illness can cause muscle damage, organ failure and death.

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Heatstroke happens when your body’s internal cooling system fails. In short, you no longer sweat enough to counter your spiking fever.

What Are the Symptoms of Heatstroke?

A very high fever (104 degrees Fahrenheit or higher) is the hallmark sign of heatstroke. Your skin tends to feel hot and dry (instead of sweaty) when you touch it. But it can feel slightly moist if you were in the middle of intense physical activity when you fell ill.

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Other heatstroke signs and symptoms can mimic those seen with heat exhaustion but worse. For instance, you may have a pounding headache, bounding pulse and fast and noisy breathing.

You may have altered mental status (AMS), which means your ability to stay awake and alert and think and behave soundly changes greatly. This happens because heatstroke can affect your brain health.

As such, you may show overt AMS signs such as:

  • Agitation or irrational or aggressive behavior
  • Coma (loss of consciousness)
  • Delirium
  • Disorientation
  • Drowsiness
  • Hallucinations
  • Seizures
  • Slurred speech

How Is Heatstroke Treated?

If you suspect someone has heatstroke, call 911 or your local emergency medical services (EMS). First aid for heatstroke involves cooling down the same way you would with heat exhaustion with a few added or omitted measures.

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Heatstroke amplifies the risk of choking due to profound changes in mental status. Therefore, don’t give them:

  • Fluids to drink, unless told by EMS or the treating ER doctor to do so
  • Medicines, including pain relievers

If they’re unconscious but breathing and not gasping for air, do:

  • Clear airway by taking out anything from their mouth you can see and remove easily.
  • Place them in the recovery position (side-lying with arms and legs bent and stacked on top of each other, chin up and mouth facing downward to drain fluids that can cause them to choke). 
  • Watch their breathing carefully.
  • Perform cardiopulmonary resuscitation, if needed.

EMS and ER staff will continue to bring the person’s temperature down, replenish lost body fluids and electrolytes and other heat illness treatments as needed. These include:

  • IV fluids
  • Immersion in an ice [or cold] water bath
  • Evaporation cooling techniques such as misting cool water on them while warm air blows water dry
  • Ice packs placed against armpits, groin, neck and torso
  • Special cooling blanket
  • Medicine [such as a muscle relaxant] to stop shivering, if needed, as this response to chills can hamper treatment

How to Prevent Heat Illness

Heat illness prevention starts with a safety plan. Aim to:

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  • Hydrate throughout your day with healthy fluids, especially before, during and after being active.
  • Stay indoors in an air-conditioned building or in front of a fan.
  • Wear lightweight and loose-fitted clothing.
  • Also wear light-colored clothing and wide-brimmed hat while outdoors.
  • Stay in the shade when outdoors.
  • Avoid working out or engaging in heavy physical activity in hot or humid climates.
  • Carry out your activity during cooler times of the day such as in the morning or evening, if you must be active when the weather’s hot.
  • Pace your activity, starting slowly and adding to it gradually.
  • Take extra precautions if you have health conditions or take medicines that impair how your body regulates heat.

Also, don’t leave your kids, pets or anyone else in a hot car. Make sure each passenger gets out safely before you make your way elsewhere.

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