By Peter Kummerfeldt
The challenges of functioning effectively in a cold environment are directly related to the ambient temperature and the wind. These challenges include dehydration, hypothermia, and a variety of other, typically non-life-threatening, medical conditions such as frostbite, trench foot, immersion foot, and chilblains.
While accurate numbers are difficult to come by it is estimated that about 600 people die each year from accidental hypothermia. Many of these, about 50%, are elderly. As with heat challenges, the emphasis needs to be an awareness of the environmental threats to your safety, on early recognition of what is happening physiologically to your body, and then an effective treatment if that becomes necessary.
Dehydration. Hypothermia and frostbite, especially hypothermia, tend to dominate any discussion on cold-weather medical issues, however dehydration is a much more likely challenge to someone working or recreating in the outdoors during the colder periods of the year. Cold-induced diuresis (an increase in the need to urinate resulting from vasoconstriction), a suppressed thirst mechanism, and the lack of readily accessible water, combine to make dehydration a significant problem in cold environments. Surprisingly, in cold environments sweating can also result in significant water loss. Despite the cold temperatures, bulky layers of clothing when combined with exercise results in elevated core temperatures, vasodilation, and sweat production. Drink enough water to keep your pee clear – or nearly so!
Accidental Hypothermia isdefined as a decrease in body core temperature below 98.6° F. as a result of your body’s inability to produce enough heat to replace the heat that is being lost to the environment in cold, wet and windy conditions. Any decrease of body temperature below normal reduces your ability to function properly. The inability to maintain normal body temperature can result from the lack of protective clothing, insufficient food needed to generate heat, dehydration, illness, medications, the consumption of alcohol, and sleep deprivation. All of these factors increase the rate at which heat is lost through evaporation, convection, radiation, and conduction.
For purposes of simplicity, hypothermia can be divided into three phases:
- Mild hypothermia. The patient is alert, verbal, and actively shivering with normal vital signs.
- Moderate hypothermia. The patient is still verbal, however will have difficulty understanding verbal commands. Shivering is violent, hand and eye movements are uncoordinated, and walking is difficult.
- Extreme hypothermia. Shivering has stopped. The patient is unresponsive to pain and barely conscious. Their metabolism has slowed and their vital signs will be hard to detect or measure.
General Treatment. Since it is unlikely that the equipment needed to accurately measure the patient’s core temperature will be available, the assessment of the patient’s condition will have to be accomplished using the other more visible signs and symptoms. Simply put, if the patient is shivering they are either mildly or moderately hypothermic and aggressive re-warming should be initiated. If they are obviously very cold and no shivering is noticed they are extremely hypothermic and should be handled very carefully. Extremely hypothermic people are very susceptible to heart arrhythmias – rough handling can trigger ventricular fibrillation, (the heart is beating but it is not pumping blood) and death will follow. In this situation it is better to protect the patient, limiting further heat loss as best possible, and then go for help. Under field conditions re-warming a very cold person may be very difficult to accomplish and, at a practical level, minimizing further heat loss in conjunction with whatever passive re-warming is possible (hot water bottles, chemical heat pads etc.) may be all that can be done for the patient.
Prevention is always the best course of action. Put another way, “It is always easier to prevent a problem than it is to treat a problem.” Don’t wait until you or someone else is hypothermic – recognize the environmental conditions that cause it – cool to cold temperatures, windy and wet conditions, and protect yourself from those conditions.
To prevent hypothermia abide by the following recommendations:
- Always travel with a buddy. Hypothermia is insidious. You may not be aware that you are becoming hypothermic but your traveling companion may notice something is not right with you.
- Either wear or have with you the clothing you need to keep yourself warm and dry. Your clothing must keep you warm and dry when you are inactive – i.e. sitting out the night under a tree waiting for the sun to rise. Do not underestimate the impact of wind to rob you of body heat. Avoid cotton clothing; instead wear any synthetic fabric against your skin. Polyester, for example, is hydrophobic and facilitates the movement of water vapor through your clothing to the outside. Pay particular attention to protecting the head, hands, and feet.
- Eat for heat. Carbohydrates produce more heat than protein and it is produced quicker.
- If wet, and replacement clothing is available, change into dry clothing. If wet and no additional clothing is available – wrap up in any material (thermal blanket, tarp etc.) and get out of the wind. Create a vapor barrier around yourself or your patient.
- Cold people are often dehydrated, sometimes very dehydrated. Assuming that they can swallow, rehydrate a patient by feeding them warm sickly sweet fluids to fuel shivering!
Becoming a victim of the cold is not limited to just those who venture to the high latitudes, the arctic or antarctic, or those who climb the world’s tallest mountains. Dehydration and hypothermia can occur anywhere a poorly protected person is exposed to cold, wet, or windy environments and where water is in short supply. Prevention is always the best course of action, but prevention is dependent on recognizing the threats to your safety – pay attention!