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Outdoor Action Guide To
Monday March 31, 2025 by Rick Curtis Traveling in cold weather conditions can be life threatening. The information provided here is designed for educational use only and is not a substitute for specific training or experience. Princeton University and the author assume no liability for any individual's use of or reliance upon any material contained or referenced herein. Medical research on hypothermia and cold injuries is always changing knowledge and treatment. When going into cold conditions it is your responsibility to learn the latest information. The material contained in this workshop may not be the most current. How We Lose Heat to the Environment
Example: Generally conductive heat loss accounts for only about 2% of overall loss. However, with wet clothes the loss is increased 5x.
Cold Challenge - (negative factors)
Heat Retention - (positive factors)
Heat Production - (positive factors)
Total = Heat Production
Heat Retention + Heat Production less than Cold Challenge = Hypothermia InsulationBody FatSurface to Volume ratioShell to Core shunting ExerciseShivering TemperatureWetnessWind Your Body Core Temperature1. Heat is both required and produced at the cellular level. The environment acts as either a heating or a cooling force on the body. The body must be able to generate heat, retain heat, and discharge heat depending on the body activity and ambient external temperature.
2. Body temperature is a measure of the metabolism - the general level of chemical activity within the body.
3. The hypothalamus is the major center of the brain for regulating body temperature. It is sensitive to blood temperature changes of as little as 0.5 degrees Celsius and also reacts to nerve impulses received from nerve endings in the skin.
4. The optimum temperature for chemical reactions to take place in the body is 98.6 degrees F. Above 105 F many body enzymes become denatured and chemical reactions cannot take place leading to death. Below 98.6 F chemical reactions slow down with various complications which can lead to death.
5. Core = the internal body organs, particularly the heart, lungs, and brain.Periphery = the appendages, skin, and muscle tissue.
6. Core temperature is the temperature that is essential to the overall metabolic rate of the body. The temperature of the periphery is not critical.
How Your Body Regulates Core Temperature1. Vasodilation - increases surface blood flow, increases heat loss (when ambient temperature is less that body temperature). Maximal vasodilation can increase cutaneous blood flow to 3000 ml/minute (average flow is 300-500 ml/minute).
2. Vasoconstriction - decreases blood flow to periphery, decreases heat loss. Maximal vasoconstriction can decrease cutaneous blood flow to 30 ml/minute.
3. Sweating - cools body through evaporative cooling
4. Shivering - generates heat through increase in chemical reactions required for muscle activity. Visible shivering can maximally increase surface heat production by 500%. However, this is limited to a few hours because of depletion of muscle glucose and the onset of fatigue.
5. Increasing/Decreasing Activity will cause corresponding increases in heat production and decreases in heat production.
6. Behavioral Responses - putting on or taking off layers of clothing will result in heat regulation
Hypothermia1. Hypothermia - "a decrease in the core body temperature to a level at which normal muscular and cerebral functions are impaired." - Medicine for Mountaineering
2. Conditions Leading to Hypothermia
3. What are "hypothermia" temperatures
4. Signs and Symptoms of Hypothermia
a. Watch for the "-Umbles" - stumbles, mumbles, fumbles, and grumbles which show changes in motor coordination and levels of consciousness
b. Mild Hypothermia - core temperature 98.6 - 96 degrees F
c. Moderate Hypothermia - core temperature 95 - 93 degrees F
d. Severe Hypothermia - core temperature 92 - 86 degrees and below (immediately life threatening)
e. Death from Hypothermia
5. How to Assess if someone is Hypothermic
The basic principles of rewarming a hypothermic victim are to conserve the heat they have and replace the body fuel they are burning up to generate that heat. If a person is shivering, they have the ability to rewarm themselves at a rate of 2 degrees C per hour.
Mild - Moderate Hypothermia1. Reduce Heat Loss
2. Add Fuel & Fluids
It is essential to keep a hypothermic person adequately hydrated and fueled.
a. Food types
b. Food intake
c. Things to avoid
3. Add Heat
1. Reduce Heat Loss
2. Add Fuel & Fluids
3. Add Heat
Heat can be applied to transfer heat to major arteries - at the neck for the carotid, at the armpits for the brachial, at the groin for the femoral, at the palms of the hands for the arterial arch.
Is a situation in which the core temperature actually decreases during rewarming. This is caused by peripheral vessels in the arms and legs dilating if they are rewarmed. This dilation sends this very cold, stagnate blood from the periphery to the core further decreasing core temperature which can lead to death. In addition, this blood also is very acetic which may lead to cardiac arrythmias and death. Afterdrop can best be avoided by not rewarming the periphery. Rewarm the core only! Do not expose a severely hypothermic victim to extremes of heat.
CPR & HypothermiaWhen a person is in severe hypothermia they may demonstrate all the accepted clinical signs of death:
But they still may be alive in a "metabolic icebox" and can be revived. You job as a rescuer is to rewarm the person and do CPR if indicated. A hypothermia victim is never cold and dead only warm and dead. During severe hypothermia the heart is hyperexcitable and mechanical stimulation (such as CPR, moving them or Afterdrop) may result in fibrillation leading to death. As a result CPR may be contraindicated for some hypothermia situations:
1. Make sure you do a complete assessment of heart rate before beginning CPR. Remember, the heart rate may be 2-3/minute and the breathing rate 1/30 seconds. Instituting cardiac compressions at this point may lead to life-threatening arrythmias. Check the carotid pulse for a longer time period (up to a minute) to ascertain if there is some slow heartbeat. Also, even though the heart is beating very slowly, it is filling completely and distributing blood fairly effectively. External cardiac compressions only are 20-30% effective. Thus, with its severely decreased demands, the body may be able to satisfy its circulatory needs with only 2-3 beats per minute. Be sure the pulse is absent before beginning CPR. You will need to continue to do CPR as you rewarm the person.
2. Ventilation may have stopped but respiration may continue - the oxygen demands for the body have been so diminished with hypothermia that the body may be able to survive for some time using only the oxygen that is already in the body. If ventilation has stopped, artificial ventilation may be started to increase available oxygen. In addition, blowing warm air into the persons lungs may assist in internal rewarming.
3. CPR Procedures
Tissue temperature in cold weather is regulated by two factors, the external temperature and the internal heat flow. All cold injuries described below are intimately connected with the degree of peripheral circulation. As peripheral circulation is reduced to prevent heat loss to the core these conditions are more likely to occur.
1. Factors influencing cold injuries
2. Cold-induced Vasodilation - When a hand or foot is cooled to 59 degrees F, maximal vasoconstriction and minimal blood flow occur. If cooling continues to 50 degrees, vasoconstriction is interrupted by periods of vasodilation with an increase in blood and heat flow. This "hunting" response recurs in 5-10 minute cycles to provide some protection from cold. Prolonged, repeated exposure increases this response and offers some degree of acclimatization. Ex. Eskimos have a strong response with short intervals in between.
3. Pathophysiology of Tissue Freezing - As tissue begins to freeze, ice crystals are formed within the cells. As intracellular fluids freeze, extracellular fluid enters the cell and there is an increase in the levels of extracellular salts due to the water transfer. Cells may rupture due to the increased water and/or from tearing by the ice crystals. Do not rub tissue; it causes cell tearing from the ice crystals. As the ice melts there is an influx of salts into the tissue further damaging the cell membranes. Cell destruction results in tissue death and loss of tissue. Tissue can't freeze if the temperature is above 32 degrees F. It has to be below 28 degrees F because of the salt content in body fluids. Distal areas of the body and areas with a high surface to volume ratio are the most susceptible (e.G ears, nose, fingers and toes - this little rhyme should help remind you what to watch out for in yourself and others).
4. Cold Response
5. Frostnip
Treatment
6. Frostbite
Treatment
7. Rewarming of Frostbite
8. Special Considerations for Frostbite
9. Trench Foot - Immersion Foot
Trench foot is a process similar to chillblains. It is caused by prolonged exposure of the feet to cool, wet conditions. This can occur at temperatures as high as 60 degrees F if the feet are constantly wet. This can happen with wet feet in winter conditions or wet feet in much warmed conditions (ex. Sea kayaking). The mechanism of injury is as follows: wet feet lose heat 25x faster than dry, therefore the body uses vasoconstriction to shut down peripheral circulation in the foot to prevent heat loss. Skin tissue begins to die because of lack of oxygen and nutrients and due to buildup of toxic products. The skin is initially reddened with numbness, tingling pain, and itching then becomes pale and mottled and finally dark purple, grey or blue. The effected tissue generally dies and sluffs off. In severe cases trench foot can involve the toes, heels, or the entire foot. If circulation is impaired for > 6 hours there will be permanent damage to tissue. If circulation is impaired for > 24 hours the victim may lose the entire foot. Trench Foot cuases permanent damage to the circulatory system making the person more prone to cold related injuries in that area. A similar phenomenon can occur when hands are kept wet for long periods of time such as kayaking with wet gloves or pogies. The damage to the circulatory system is known as Reynaud's Phenomenon.
Treatment and Prevention of Trench foot
10. Chillblains
11. Avoiding Frostbite and Cold related Injuries
12. Eye Injuries
a. Freezing of Cornea
b. Eyelashes freezing together
c. Snowblindness
Symptoms
Treatment
BIBLIOGRAPHY
Are You Running A Fever? 98.6°F May No Longer Be The Baseline
For seemingly forever, we've been told 98.6 degrees Fahrenheit is the standard for a normal body temperature. However, recent studies suggest that the number may be outdated.
According to research, the average body temperature has dropped to around 97.9°F, with variations based on age, health conditions and even race and gender. The discussion gained traction recently when a viral TikTok video questioned whether 99.1°F should count as a fever.
It turns out, they have a point.
A history lesson on 98.6°FThe idea that 98.6°F is "normal" comes from 19th-century German physician Carl Reinhold August Wunderlich, who took more than a million temperature readings and set the standard. But that was nearly 200 years ago, and our bodies — and the world — have changed.
"We are not the same people that we were in the middle of the 19th century," Dr. Julie Parsonnet, the George DeForest Professor of Medicine and a public health researcher at Stanford Medicine, told USA Today.
Harvard study finds new 'normal'A 2017 Harvard Medical School study analyzed data from more than 35,000 patients and found the average body temperature is 97.9°F, ranging from 97.2°F to 98.4°F.
The study also found body temperature varies by age, gender and medical conditions. Older adults tend to run cooler, African American women the warmest, and older white men the coolest. People with hypothyroidism often have lower temperatures, while those with cancer or higher BMIs tend to run warmer.
ExploreHow to reduce your cold and flu symptoms this seasonWhy we may be running coolerThe decline in body temperature is most likely linked to improvements in health and lifestyle, according to a 2020 study published in the open-access journal eLife.
In the 19th century, people faced more infections, harsh living conditions, and limited medical care, which kept their immune systems constantly active — raising their internal temperatures. Thanks to modern medicine, our bodies no longer have to work as hard to fight off disease, allowing temperatures to drop slightly.
"Physiologically, we're just different from what we were in the past," Parsonnet said in a press release, the Atlanta Journal-Constitution previously reported. "The environment that we're living in has changed, including the temperature in our homes, our contact with microorganisms and the food that we have access to."
ExploreFeeling nauseous? These home remedies are doctor approvedSo, what's considered a fever?Doctors traditionally define a fever as 100.4°F or higher. But if your normal temperature is lower, even 99.1°F might make you feel unwell. Instead of focusing on one number, experts recommend tuning into your body's norm.
Here's what to do if you start feeling feverish, according to WebMD.
Hydrate: Dehydration makes everything worse, so drink plenty of fluids.
Rest: Give your body time to recover, even if your temp isn't considered very high.
Monitor symptoms: Fever is just one clue. Watch for chills, aches and fatigue.
Call a doctor if symptoms worsen: If you feel terrible despite a "normal" temp, don't ignore it.
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7 Fever Facts Every Parent And Caregiver Should Know
The complete guide to recognizing, treating, and knowing when a fever requires medical attention
The human body's internal thermostat operates with remarkable precision, maintaining core temperature within a narrow range that supports optimal function. When that temperature rises above normal parameters, it signals that something unusual is happening within our systems. Fever represents one of the body's most common defensive responses, yet it often triggers anxiety, especially when affecting loved ones or vulnerable family members.
While reaching for a thermometer provides the most definitive answer to whether someone is experiencing a fever, understanding the broader constellation of symptoms and signals can help you make informed healthcare decisions even without measurement tools at hand. This comprehensive guide explores fever's essential characteristics, management strategies, and crucial warning signs that should prompt professional consultation.
What exactly constitutes a feverThe medical definition of fever centers on a specific threshold: when body temperature rises to 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, healthcare professionals classify it as a fever. This elevation from normal temperature typically indicates that the body has activated its immune response to address an underlying issue, most commonly an infection.
However, this seemingly straightforward definition contains important nuances. Normal body temperature actually varies between individuals and fluctuates throughout the day, with most people running slightly cooler in the morning and warmer in late afternoon and evening. The often-cited "normal" temperature of 98.6°F represents an average rather than a universal constant.
Age further complicates temperature assessment. Infants and young children typically maintain higher baseline temperatures than adults, while older adults often run cooler than the general population. This variation means that what constitutes a significant temperature elevation might differ across age groups, with elderly individuals potentially experiencing fever at readings that might seem normal in younger adults.
The temperature measurement method also influences readings, with rectal temperatures typically reading higher than oral measurements, which in turn run higher than temperatures taken at the armpit. When using a temporal artery or forehead scanner, readings may vary based on environmental conditions and proper technique.
Recognizing fever without a thermometerWhile clinical confirmation of fever requires temperature measurement, several recognizable signs and symptoms can alert you to its presence when a thermometer isn't available. The body provides multiple indicators when fighting infection or dealing with inflammatory responses.
The most common telltale signs include feeling noticeably warm to the touch, particularly across the forehead and cheeks. Many people experience pronounced temperature contrast when someone places a hand on their skin versus touching others or surfaces in the same environment.
Alongside feeling warm, fever often produces a constellation of full-body symptoms. Unexplained fatigue or weakness occurs as the body diverts energy toward immune function rather than normal activities. Many people report significant appetite changes, typically manifesting as reduced interest in food regardless of the time since their last meal.
Perhaps most distinctive are the seemingly contradictory thermal sensations that often accompany fever. Despite running objectively warmer, many individuals experience pronounced chills, sometimes escalating to visible shivering despite warm ambient temperatures or being covered with blankets. This paradoxical response happens because the brain temporarily resets its target temperature higher during infection, making the current body temperature feel relatively cool in comparison.
Some people also report heightened sensitivity to environmental temperatures, finding normal room conditions suddenly uncomfortable or experiencing dramatic shifts between feeling overheated and chilled within short timeframes. Skin may appear flushed, particularly across the face, and feel unusually dry to the touch.
Other common accompanying symptoms include headache, general malaise (feeling unwell without specific complaints), muscle aches, and sometimes mild confusion or difficulty concentrating. While none of these signs definitively confirms fever without temperature measurement, their combined presence strongly suggests elevated body temperature, particularly when they develop suddenly or in conjunction with other signs of illness.
Typical fever duration and patternsFever duration typically correlates strongly with its underlying cause, making the timeline an important diagnostic clue for healthcare providers. Most common viral infections produce fevers lasting between two and three days, though individual variation exists based on specific pathogens and personal immune response.
Some fever patterns follow predictable trajectories that help identify their source. Bacterial infections often produce sustained high fevers until appropriate treatment begins, while certain viral illnesses create characteristic fever curves. For instance, influenza frequently causes rapidly spiking temperatures that remain elevated for several days before gradually resolving.
Other infections produce distinctive fever patterns that help medical professionals narrow diagnosis. Some parasitic infections create cyclical fevers that rise and fall at regular intervals. Certain autoimmune conditions cause persistent low-grade fevers that can last weeks or months, while some cancers produce intermittent unexplained temperature elevations.
For most common illnesses, however, fever represents a self-limiting symptom that resolves as the body successfully combats infection. The typical timeline puts most fever resolution within 72 hours of onset, though lingering fatigue and weakness might persist after temperature normalizes.
When fever continues beyond three days, extends beyond the expected timeline for a diagnosed condition, or returns after apparent resolution, these patterns warrant additional medical evaluation. Persistent or recurrent fevers sometimes indicate that the initial infection hasn't been fully cleared, that complications have developed, or potentially that another underlying condition requires attention.
Effective home management strategiesMost fevers respond well to straightforward home care strategies focused on comfort and support while the body fights infection. These approaches don't necessarily eliminate fever entirely, nor should that be the primary goal, as elevated temperature serves important immune functions in many cases.
Rest represents perhaps the most essential fever management strategy. The immune response requires significant energy expenditure, and limiting physical activity allows the body to direct resources toward fighting infection rather than supporting optional activities. Creating a comfortable recovery environment with appropriate room temperature, minimal disruptions, and accessible necessities facilitates this rest.
Maintaining proper hydration becomes critically important during fevers, as elevated body temperature increases fluid loss through perspiration and respiration. Clear liquids including water, diluted juice, and electrolyte replacement drinks help prevent dehydration. For those with reduced appetite, consuming small amounts of fluid frequently often proves more successful than attempting larger quantities less often.
Over-the-counter medications including acetaminophen and ibuprofen can help reduce fever and alleviate discomfort, though they should be used judiciously rather than automatically at the first sign of temperature elevation. These medications can mask symptoms without addressing underlying causes, potentially delaying appropriate medical care if needed.
When using fever-reducing medications, following packaging guidelines for appropriate dosing based on age and weight remains essential. Parents should be particularly cautious with children, using pediatric formulations and avoiding aspirin for those under 18 years due to association with Reye's syndrome, a rare but serious condition.
Other supportive measures include dressing in lightweight, breathable clothing that allows excess heat to dissipate, and using lightweight blankets that can be easily added or removed as comfort needs change. Cool (not cold) compresses applied to the forehead, neck, armpits, or groin areas can provide comfort during high fevers, though aggressive cooling measures like ice baths or alcohol rubs should be avoided as they can cause rapid temperature changes and additional discomfort.
When fever requires medical attentionWhile most fevers resolve with basic home care, certain situations warrant prompt medical evaluation. Understanding these warning signs helps distinguish between self-limiting conditions and those requiring intervention.
For adults, fever exceeding 103°F (39.4°C) generally warrants medical attention, particularly when accompanied by severe headache, unusual rash, significant neck stiffness, persistent vomiting, difficulty breathing, chest pain, or confusion. These combinations may indicate serious conditions including meningitis, pneumonia, or systemic infections requiring rapid treatment.
Children's fevers demand different assessment thresholds. For infants under three months, any temperature over 100.4°F (38°C) requires immediate medical evaluation, as newborns have immature immune systems and limited ability to combat infections. Between three months and three years, temperatures above 102.2°F (39°C) that persist despite fever-reducing medication or last longer than two days warrant professional assessment.
Duration provides another important consideration regardless of age. Any fever persisting beyond three days, returning after resolution, or following recent international travel, hospitalization, or antibiotic treatment deserves medical attention. These patterns sometimes indicate resistant infections or complications requiring specific interventions.
Equally important to temperature readings are behavioral and functional changes. Difficulty waking, unusual irritability, refusing to drink fluids, showing signs of dehydration, or experiencing pain when urinating all represent concerning developments that should prompt medical evaluation regardless of specific temperature readings.
For individuals with compromised immune systems due to medication, chronic illness, or advanced age, fever often signals potentially serious infections that might progress rapidly without intervention. These populations benefit from lower thresholds for seeking medical care, often at the first sign of elevated temperature or illness.
The science behind fever's protective roleWhile discomfort naturally leads many to view fever negatively, scientific understanding increasingly recognizes fever as an important defensive mechanism rather than simply a symptom requiring elimination. This shifting perspective influences modern approaches to fever management.
Research demonstrates that moderately elevated temperatures actually enhance immune function through multiple mechanisms. Higher temperatures accelerate white blood cell production and movement, increase antibody effectiveness, and create less hospitable environments for many pathogens. Some viruses and bacteria replicate more slowly at elevated temperatures, giving the immune system advantage in clearing infections.
These benefits explain why completely suppressing fever might potentially prolong certain illnesses. Studies suggest that routine fever reduction for otherwise healthy individuals with mild to moderate temperature elevations provides comfort but doesn't necessarily shorten illness duration and might occasionally extend it.
This understanding has shifted medical approaches toward managing fever's discomfort while respecting its biological purpose. Current guidelines generally recommend treatment focused on comfort rather than automatically suppressing all temperature elevations, particularly for mild to moderate fevers in otherwise healthy individuals.
However, this balanced approach doesn't diminish the importance of monitoring and appropriate intervention. Very high
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