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Hypothermia is a potentially life-threatening condition. It results when your body loses heat faster than it can produce heat. Awareness of the causes, symptoms and prevention measures can help you avoid this medical emergency.
Core Body Temperature
Heat is required and produced at the cellular level. Your core body temperature is the level of heat of your internal organs, particularly the heart, lungs and brain. It is also the temperature that is essential to the overall metabolic rate of your body. For normal function, your body must be able to generate heat, retain heat and discharge heat, depending on your level of physical activity and ambient external temperature.
Your body temperature is a measurement of metabolism or the general level of chemical activity in the body. The optimal body temperature is 98.6 degrees Fahrenheit. When body temperature drops below 98.6 degrees Fahrenheit, chemical reactions slow down. This leads to various complications, even death. (1)
Degrees of Hypothermia
Hypothermia occurs when the core body temperature falls below 95 degrees Fahrenheit. Normal muscular and cerebral functions are impaired. Hypothermia ranges from mild to moderate to severe.
Mild hypothermia occurs with a core body temperature of between 98.6 and 96 degrees Fahrenheit. Symptoms include uncontrollable shivering, faster breathing, increased heart rate and blood pressure, difficulty speaking, confusion, loss of coordination and fatigue.
The most common cause of mild hypothermia is exposure to cold temperatures without appropriate warm, protective clothing, and immersion in cold water. Mild therapeutic hypothermia is used to improve the neurologic outcome in patients, who have been successfully resuscitated following a cardiac arrest. (2)
Moderate hypothermia occurs with a core body temperature of between 95 to 93 degrees Fahrenheit. Symptoms include uncontrollable shivering, impaired ability to concentrate or think clearly, and confusion, and irrational behavior, loss of coordination, slurred speech, drowsiness and slow, shallow breathing. (3)
Prolonged exposure to cold temperatures without wearing warm clothing quickly leads to moderate hypothermia. Individuals who work outdoors in freezing and windy winter conditions, folks who are shoveling their driveways and walkways and skiers or hikers are at risk for hypothermia and must dress warmly.
Accidental falls into cold water, either in a boating accident or falling through a thin layer of ice, is a risk factor. Inadequate heating in living spaces or air conditioning that is too cold can lead to moderate hypothermia in the elderly and infants.
Individuals with impaired mental function, like someone with Alzheimer’s disease, may not dress appropriately for the weather, wonder from home and be at risk for hypothermia.
Certain medical conditions, such as hypothyroidism, and medications, including antidepressants, antipsychotics and sedatives, can alter the body’s ability to regulate temperature. (4)
Severe hypothermia results when the core body temperature drops to between 92 to 86 degrees Fahrenheit. It is a life-threatening situation that requires immediate medical attention.
Symptoms include violent shivering that alternates with pauses. The intervals of pausing get longer until shivering finally stops. The person falls to the ground and curls up in a fetal position to conserve heat. Muscles become rigid, the pupils dilate, the skin is pale and the pulse rate drops.
At a core body temperature of 90 degrees Fahrenheit, the body moves into hibernation, shutting down all peripheral blood flow and reduces breathing rate and heart rate. When a person’s temperature drops to 86 degrees, the person appears dead, but is still alive.
Individuals who are homeless or those strained in extreme weather conditions have an increased risk for developing severe hypothermia.
Prevention
Prevent hypothermia by dressing warmly, wear a hat and cover your hands with mittens instead of gloves. Avoid overexertion. The combination of wet clothing from sweating and cold temperature causes you to lose heat quickly.
Dress in layers. Wool, silk and polypropylene inner layers hold body heat better than cotton does. Get out of wet clothing as quickly as possible.
Whenever you travel in bad weather, let someone know your destination and expected time of arrival. Keep emergency supplies, such as warm blankets, canned or dry food, a manual can opener, flashlight, bottled water and a first aid kit. Travel with a fully-charged cell phone.
If stranded, stay in your car, run your car for 10 minutes each hour to keep it warm, keep windows open slightly and make sure the exhaust pipe is not blocked with snow while the car engine is running.
Avoid drinking alcohol before going out in cold weather, while boating or before going to bed on cold nights. Any water colder than body temperature causes heat loss. When boating, always wear a life jacket. If you accidentally fall in, keep your clothes on and hold your knees to your chest to protect your trunk. (4)
Sources:
(1) Outdoor Action @ Princeton University: Outdoor Action Guide to Hypothermia and Cold Weather Injuries by Rick Curtis, Nov. 26, 2011
http://www.princeton.edu/~oa/safety/hypocold.shtml
(2) The New England Journal of Medicine: Mild Therapeutic Hypothermia to Improve the Neurologic Outcome after Cardiac Arrest, 346:549-556February 21, 2002, Nov. 26, 2011
http://www.nejm.org/doi/full/10.1056/NEJMoa012689
(3)NHS Choices: Hypothermia- Symptoms, Nov. 26, 2011
http://www.nhs.uk/Conditions/Hypothermia/Pages/Symptoms.aspx
(4) Mayo Clinic: Hypothermia- Risk Factors, Nov. 28, 2011
http://www.mayoclinic.com/health/hypothermia/DS00333/DSECTION=risk-factors
Reviewed November 28, 2011
by Michele Blacksberg RN
Edited by Jody Smith
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