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HYPOTHERMIA (Part 3)
- Increasing Heat Production -

Involuntary shivering is an early sign of hypothermia and its purpose is to produce heat by increasing muscular activity. Shivering can produce five times as much heat as is produced by the body at rest, but exercise produces more heat than does shivering. In addition to shivering, the body responds to the cold by making the blood vessels in the arms and legs narrower, thus reducing blood flow. Consequently, the tissues are cooler (and more susceptible to frostbite), but heat loss is also thereby reduced. As a result of constriction of the blood vessels in the extremities, blood flow is increased to the heart and brain, thereby increasing survival time. Blood viscosity is increased (the blood becomes "thick"). Blood volume and blood flow are reduced, decreasing oxygen transport to vital organs such as the brain and heart. The concentration of blood in the core of the body causes the kidneys to excrete more urine. In addition, chilled kidneys have a reduced capacity to retain fluids. These two factors cause increased water loss. Nearly all victims of hypothermia are dehydrated. This loss of water contributes to a decrease in blood volume and to an increased risk of frostbite, blood clots in the legs and pulmonary embolism. People who are dehydrated may experience fatigue, weakness and dizziness.

• EAT. When you are in a cold environment, you must increase food intake. Even without exercise, you must EAT MORE than usual in order to maintain body temperature. Food is the fuel which the body requires in order to produce more heat which will maintain body temperature. If you feel cold - eat. Eat small amounts of high-calorie food at frequent intervals (raisins, nuts, dried fruit, carbohydrates,candies).

• EXERCISE. Exercise increases the body's production of heat, especially when large muscles groups such as those in the legs are used. More exercise - more heat. Remember, the more you exercise, the more you need to eat in order to fuel all that production of energy. Exercise produces more heat than standing around shivering.
  • If you are at home and the power goes out, this is the time to do all those chores and housecleaning that you've been putting off doing. If you've removed you food from the fridge and freezer, take this opportunity to clean these appliances (remember to switch them off and to leave the doors and lids open afterward). If you are planning to stay in the cold house, there are lots of things that need to be done to make your stay more comfortable and safer. If you are planning to leave the house, there are many things that need to be done before leaving to protect the house in your absence and to make your return more pleasant. All of this activity will keep you warm. Remember to remove layers of clothing to avoid sweating and to put them back on before you start to cool down.

• DRINK. You will become dehydrated in the cold unless you drink lots of extra fluids. Do not drink alcohol and avoid caffeinated beverages since the make you urinate more (tea, coffee, cola drinks). Do not eat snow or ice since this will only serve to cool your body further. Dehydration leads to all sorts of problems, not the least of which is a decreased ability to produce heat by exercise. You know you are dehydrated if you urinate less frequently than usual, if you don't feel the need to urinate upon awakening in the morning or if your urine is a deep yellow or orange colour. Unfortunately, thirst is absent or greatly diminished in the presence of dehydration and, in a cold environment, it becomes necessary to force oneself to drink a sufficient amount of fluids:
  • Drink two litres (quarts) of fluids per day if you are engaged in mild exercise;
  • Drink three to four litres (quarts) per day if you are engaged in heavy exercise.

See also:
Part 1: Hypothermia - Introduction
Part 2: Decreasing Heat Loss
Part 4: Mild Hypothermia and Treatment
Part 5: Severe Hypothermia and Treatment

CC Austin, PhD

© 1998 SAREC - All rights reserved (Updated 98/01/21) http://www.sarec.ca/ice
Contact CC Austin, PhD, to obtain special permission to freely reproduce and distribute this safety bulletin during the current ice storm disaster.
This copyright notice must be included with all reproductions of this safety bulletin. Telephone: (514) 989-3720 Email: caustin@sarec.ca