Hypothermia

Hypothermia is a medical condition in which the victim's core body temperaturehas dropped to significantly below normal and normal metabolismbegins to be impaired. This begins to occur when the core temperaturedrops below 35 degrees Celsius(95 degrees Fahrenheit). If body temperature falls below 32 °C (90 °F), the condition can become critical and eventually fatal. Body temperatures below 27 °C (80 °F) are almost uniformly fatal, though body temperatures as low as 14 °C (57.5 °F) have been known to survive. The opposite condition, where temperature is too high, is hyperthermia.

For unknown reasons, people who fall critically unconscious (and arguably die, though there are some who argue that any reversible condition is not, by definition, death) in very cold water can, in rare cases, be resuscitated, even though they would be expected to have died of drowning and/or hypothermia. See Mammalian diving reflex.

Types

There are three types of hypothermia, acute, subacute, and chronic.

• Acute hypothermia is the most dangerous; the body temperature drops very swiftly, often in a matter of secondsor minutes, such as when a victim falls through an ice-covered lake.
• Subacute hypothermia occurs on a scale of hours, most commonly by remaining in a cold environment for an extended period of time.
• Chronic hypothermia is typically caused by an underlying disease.

Symptoms

• Amnesia
• Ataxia
• Cold skin, even in torso
• Confusion, progressing to delirium
• Diuresis
• Dysarthria
• Graycomplexion(pallor)
• Hypokinesia
• Increased muscle tone
• Low blood pressure(hypotension)
• Peripheral cyanosis
• Rapid breathing (tachypnea) and heart rate(tachycardia), slowing and weakening as temperature decreases
• Shivering
• Tremor
• Uncontrollable bleeding due to reduced coagulationenzymeactivity
• Weakness

Treatment

Treatment for hypothermia involves raising the core body temperature of the victim.

The first aidresponse to someone experiencing hypothermia, however, must be made with caution.

• Do not rub or massage the casualty
• Do not give alcohol
• Do not treat any frostbite
• Do not allow the body to become vertical

Any of these actions will divert blood from the critical internal organs and will worsen the situation.

What you should do:

• Call the emergency services
• Get the patient to shelter
• If possible, put the patient in a bath with medium-temperature water, with the clothes on
• Place hot water bottles (wrapped in a cotton sock) in the patient's armpits and between their legs
• Give food and warm drinks
• Monitor the patient and be prepared to give Cardio-pulmonary resuscitation.
• Remove wet clothing if and only if a dry change is available

If the hypothermia has become severe, notably if the patient is incoherent or unconscious, re-warming must be done under strictly controlled circumstances in a hospital. Bystanders should only remove the patient from the cold environment, give warm drinks (not too warm because it can lead to temperature shock) and get the patient to advanced medical care as quickly as possible.

In hypothermia, the heart becomes extremely "irritable", and sudden re-warming can provoke cardiac arrhythmias, irregular beating of the heart in which blood isn't pumped adequately or may not be pumped at all. Common first aid wisdom in helping someone suspected of suffering from hypothermia is to treat them as if they were fragile, or made of glass — do nothing to over-stimulate the heart.

Hospital treatment

In a hospital, warming is accomplished by external techniques (blankets, warming devices) for mild hypothermia and by more invasive techniques such as warm intravenous fluids or even lavage (washing) of the bladder, stomach, chest and abdominal cavities with warmed fluids for severely hypothermic patients. These patients are at high risk for arrhythmias (irregular heartbeats), and care must be taken to minimize jostling and other disturbances until they have been sufficiently warmed, as these arrhythmias are very difficult to treat while the victim is still cold. An important tenet of treatment is that a person is not dead until they are warm and dead - remarkable stories of recovery after prolonged cardiac arrest have been reported in patients with hypothermia. This is presumably because the low temperature prevents some of the cellular damage that occurs when blood flow and oxygen are lost for an extended period of time.

Prevention

In air, most heat is lost through the head, so hypothermia can be most effectively prevented by covering the head. Having appropriate clothing for the environment is another important prevention. Fluid-retaining materials like cotton, can be a hypothermia risk if the wearer gets sweaty on a cold day, then cools down and has sweat soaked clothing in the cold air. For outdoor exercise on a cold day, it is advisable to wear fabrics which can wick away sweat moisture. These include woolor synthetic fabrics designed specifically for rapid drying.

Heat is lost much more quickly in water. Children can die of hypothermia in as little as two hours in water as warm as 16°C, typical of sea surface temperatures in temperate countries such as Great Britain. Many seaside safety information sources fail to quote survival times in water, and the consequent importance of diving suits, possibly because the original research into hypothermia mortality in water was carried out in wartime Germany on unwilling subjects. There is an ongoing debate as to the ethical basis of using the data thus acquired. Information on wetsuits and safety in water can be found here.

There is considerable evidence, however, that children that drownin water near 0°C can be revived up to two hours after losing consciousness. The cold water also considerably lowers metabolism, allowing the brain to withstand a much longer period of hypoxia.

Medically induced

Hypothermia is sometimes induced deliberately as preparation for surgeryon the heart or during artificial comato increase survival chances after cardiac arrest or severe injury.

Hypothermia is also a consequence of anestheticinduction drugs and occurs to some extent every time an anesthetic is given. Anesthetic drugs produce two different effects that lead to hypothermia during surgery: They increase the width of blood vessels, vasodilation, which means that blood flows easily from the body's inner organs or core to the periphery or skin. This allows heat to be easily lost or radiated from the body. The temperature control center situated in hypothalamusis also affected by drugs causing the normal temperature control limits to be increased, compromising the body's normal cold response system.

Recent research has also shown that in patients who are resuscitated after cardiac arrest (stopping of the heart) the chance for recovery is increased if the victim is then cooled to about 33 degrees Celsius (91 °F). Patients who are cooled have better survival and better neurological recovery. This is usually accomplished by either ice-cold intravenous fluids or placement of ice packs in the patient's armpits and groin, although other methods are available. This therapy is increasingly being used in hospital emergency departmentsand intensive care units.

See also

• Fan death
• First aid
• Frostbite
• Hibernation
• Mountain rescue
• Torpor
• Winter sport

External links

• CanyonWiki:Hypothermia
• Canadian rescue workers internet site (hypothermia division)
• Hypothermia
• Hypothermia in the elderly
• http://www.hypothermia.org/
• The hypothermia database
• Windchill chart in km/h windspeeds and °C temperature measures
• Help the aged charaty's (United Kingdom) hypothermia in the elderly death information and advice/downloads etcde:Hypothermie

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This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Hypothermia Wikipedia article Hypothermia.