Hiker’s Hypothermia In The Summer? Are You Safe?

Chris at Timberline in the Adirondacks
Average read time 5 min

With my Boy Scout troop back in 2002, we were on Slide Mountain in the Catskills on a cloudy August afternoon. A woman comes hiking from Woodland Valley Campground some seven miles away and over two other mountains wearing shorts and a t-shirt. She had no additional insulation. Her lips were blue, and she was shivering. She sat alone, seemingly uninterested in the extraordinary summit she just had climbed. The temperature was about 55℉ with a stiff breeze blowing. She had an almost empty bottle of water and no food. She was experiencing Hiker’s Hypothermia.

Have you ever asked yourself: Can I get hypothermia in the summer?

You probably haven’t. But you can.

It comes as a surprise to many people to learn that most hypothermia cases occur between 30 and 50℉. On mountain summits, it is not uncommon for temperatures to be significantly lower than the valleys. When factoring in wind increases, the added windchill compounds this drop in temperature. In the backcountry, hikers, even in summer, are at risk for various reasons. One of the less known is a malady termed “Hikers Hypothermia .”

Hiker’s hypothermia is not a condition; it’s hypothermia. Hiker’s hypothermia (HH) is the outcome of a sequela of variables that cause a hiker to become hypothermic. Preventing any of the states will lessen the likelihood of the hiker becoming hypothermic. 

Factors in Hiker’s Hypothermia

Several factors may lead to HH, including exertional fatigue, poor sleep, dehydration, and negative energy balance. Also, inadequate clothing is a significant factor.

Related post: Clothing Materials for Hiking and Backpacking

Exertion

Fatigue brought on by exertion interferes with shivering and peripheral vasoconstriction, both of which help defend against hypothermia. The impact on protecting the core may have to do with the neurotransmitter norepinephrine changes, which decrease with heavy exertion. The reduction may impact peripheral vasoconstriction as a method for retaining heat.

Chronic negative energy balance

Many people use hiking and exercise and eating less, thus creating a negative energy balance to lose weight. A negative energy balance impairs the ability to defend the core. The blunted ability to protect the body happens in two ways—first, the loss of metabolically active lean-body-tissue occurs with weight loss. 

The loss of muscle mass may interfere with or limit the body’s shivering mechanism. Also, the loss of this highly active tissue lowers the resting metabolic rate. Second and more importantly is the loss of insulative body fat. 

Body fat is protective against cold, especially in water submersion. Body fat lowers the temperature when your body would need to start shivering.

Exertion and negative energy balance together

Researchers have found minimal impact on the body’s ability to protect against the cold in studies looking at caloric restriction short bouts under cold stress. The addition of overexertion stressed the body in combination with underfeeding and may have drained energy reserves. Blood glucose levels of 2.5mmol/l can shut down shivering mechanisms.

Dehydration

Water is the body’s most important nutrient, and dehydration reduces athletic performance. Impaired muscle function leads to reductions in one of the body’s most abundant heat-generating sources, physical activity.

Related post: How Much Water Should You Drink on a Hike and Why?

Sleep deprivation

Sleep and circadian rhythms are linked and are with disordered sleep; the circadian rhythms are disrupted. Circadian rhythms are involved with the body’s ability to regulate body temperature.

Related post: 10 Small Changes That Will Have A Huge Impact On Your Sleep in the Woods

Symptoms and first aid for hypothermia

  • Shivering
  • Increased heart rate
  • Urge to urinate
  • Slight incoordination of hand movements
  • Increased respiratory rate
  • Red face
  • Muscular incoordination
Adapted from Medicine For The Outdoors
  • Pale, cold, and dry skin – their skin and lips maybe blue
  • Slurred speech
  • Slow or shallow breathing
  • Tiredness or confusion
  • Vision loss
  • Inability to follow commands and poor judgment
  • Undressing
  • Apathy
  • Rapid heart rate
  • Amnesia
Adapted from Medicine For The Outdoors
  • Minimal breathing
  • Coma
  • Decreased respiratory rate
  • Decreased to no neurological reflexes
  • No voluntary motion
  • No response to pain
  • Slow heart rate and low blood pressure
  • High risk for ventricular fibrillation
Adapted from Medicine For The Outdoors
  • Poikilothermic (snake-like taking on the temperature of the environment)
  • Absence of detectable breathing
  • Absence of detectable heart rate
  • Profound Bradypnea (very slow breathing) or Bradycardia (very slow heart rate).
  • Dilated pupils
  • High risk for ventricular fibrillation
  • Looks dead
Adapted from Medicine For The Outdoors
  • Carry adequate clothing. Enough for the lowest possible temperatures for the season.
  • Bring spare clothing to change into if you get wet.
  • Use wicking, fast-drying clothing – NO cotton.
  • Stay dry.
  • Bring ample food. Eat regularly.
  • Stay hydrated.
  • Avoid exhaustion.
  • Seek shelter in extreme conditions.
Adapted from Medicine For The Outdoors

Always suspect hypothermia if a person is at risk and shows signs of altered mental status. Never leave a person with hypothermia (even mild) unattended.

Check the person’s temperature using a hypothermia thermometer.

Always treat people with hypothermia gently, especially with severe to profound conditions, as any “rough handling” or rapid warming may cause a lethal heart rhythm called ventricular fibrillation.

If the individual has wet or damp clothing on, if available, remove and gently redress them in dry clothing if there is no dry clothing, ring out the wet clothing and redress.

Add additional layers such as a sleeping bag, blankets, or some form of plastic to hold in body heat. Don’t forget to cover the head, hands, and feet.

Put the victim in a shelter that protects from the wind.

Mild to moderate hypothermia (if the victim is coherent and can swallow) allow the victim to drink warm liquids with carbohydrates (e.g., cocoa).

Rewarm the central part of the body using body warmers or warmed water bottles; do not put directly on the person’s skin as this may cause burns.

Do not actively rewarm the limbs.

Do not use massage to rewarm.

Read this article for handling profound hypothermia in the backcountry.

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