A fall in body temperature to a dangerously low level
- May occur at any age but most common in babies and elderly people
- Homelessness and outdoor activities in cold climates are risk factors
- Gender and genetics are not significant factors
Hypothermia is a condition that occurs when the body’s temperature, normally about 37°C (98.6°F), falls below 35°C (95°F). The body normally has various warming mechanisms, including shivering, that replace lost heat. However, if the environment is too cold or if the body’s warming mechanisms fail, hypothermia develops. Hypothermia may be associated with frostbite and, if it is extreme, can be life-threatening.
Who is at risk?
Hypothermia is particularly common in climbers and walkers who are inadequately dressed for cold weather. People who are homeless in cold weather are also vulnerable. In addition, people who have reduced awareness of low temperatures due to alcohol or drug abuse may not realize they need to protect themselves and may develop hypothermia.
Certain disorders increase the risk of developing hypothermia. For example, hypothyroidism slows down the body’s functions and reduces the body temperature. People whose mobility is reduced following a stroke or because of a disorder such as arthritis generate little body heat and are also more susceptible to hypothermia.
Elderly people are particularly at risk of developing hypothermia. As the body ages, it becomes less able to maintain its normal body temperature in cold conditions. Elderly people may also be less aware of the cold and do not always notice if their body temperature drops. In some cases, dementia may reduce an elderly person’s awareness of temperature changes.
Babies are susceptible to hypothermia because they lose heat rapidly and, like elderly people, cannot easily maintain their body temperature.
In all cases, the rate of heat loss and therefore the risk of hypothermia is increased in high winds or wet conditions, and hypothermia may develop particularly quickly when a person is immersed in cold water.
What are the symptoms?
The symptoms of hypothermia usually develop gradually over hours or days but may develop in minutes in someone immersed in cold water or exposed to high winds. The person may not feel cold. Symptoms may include:
Slow, clumsy movements.
Confusion, impaired judgment, and slow reactions.
Blue, cold hands and feet.
As the body temperature drops further, these symptoms become more obvious. In addition, the lips may turn blue, delirium or loss of consciousness may develop, and the heart may develop an abnormal rhythm (see Arrhythmias) or, eventually, even stop beating (see Cardiac arrest).
What can I do?
If you are with someone who has mild hypothermia, move him or her to a warm, sheltered place. If necessary, help remove damp clothes and replace them with warm, dry clothing, including a hat. Wrap the person in a warm blanket, and, if he or she is fully conscious, give him or her a warm, nonalcoholic drink. Do not give the person alcohol because it increases heat loss from the surface of the skin and can therefore exacerbate the condition. If hypothermia is more severe, or if the person becomes unconscious, call for medical help as soon as possible.
If you are stranded in a remote place with a person with severe hypothermia, you should follow as many of the afore mentioned measures as possible until help arrives. If possible, get into a survival or sleeping bag together. Your body heat will help to warm the person up.
What might the doctor do?
The doctor will assess the degree of hypothermia using a rectal thermometer that can record low temperatures. People with severe hypothermia need slow rewarming in hospital, usually in an intensive therapy unit. Most people with mild to moderate hypothermia recover fully. The outlook is best for young, otherwise healthy people.
In most cases, hypothermia can be prevented by self-help measures, such as dressing warmly and keeping moving in cold weather.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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