Hypothermia 146879 224495205 2008-07-09T02:45:18Z One Salient Oversight 63037 /* Prevention */ 80F made into 26 C and explanation qualified. {{wiktionary}} {{Infobox_Disease | Name = {{PAGENAME}} | Image = | Caption = | DiseasesDB = 6542 | ICD10 = {{ICD10|T|68||t|66}} | ICD9 = {{ICD9|991.6}} | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = med | eMedicineTopic = 1144 | MeshID = D007035 | }} '''Hypothermia''' is a condition in which an organism's temperature drops below that required for normal [[metabolism]] and bodily functions. In [[warm-blooded]] animals, core [[body temperature]] is maintained near a constant level through biologic [[homeostasis]]. But when the body is exposed to cold its internal mechanisms may be unable to replenish the heat that is being lost to the organism's surroundings. Hypothermia is the opposite of [[hyperthermia]], the condition which causes [[heat exhaustion]] and [[heat stroke]]. == Symptoms == Normal body temperature in [[human]]s is 37°C. Hypothermia can be divided in three stages of severity. In stage 1, body temperature drops by 1-2°C below normal temperature (35-38°C). Mild to strong [[shivering]] occurs.<ref name=sterba>{{cite journal |author=Sterba, JA |title=Field Management of Accidental Hypothermia during Diving. |journal=US Naval Experimental Diving Unit Technical Report |volume=NEDU-1-90 |date=[[1990]] |url=http://archive.rubicon-foundation.org/4248 |accessdate=2008-06-11 }}</ref><ref name=francis>{{cite journal |author=Francis, TJR |title=Immersion hypothermia. |journal=South Pacific Underwater Medicine Society journal |volume=28 |issue=3 |date=[[1998]] |issn=0813-1988 |oclc=16986801 |url=http://archive.rubicon-foundation.org/5975 |accessdate=2008-06-11 }}</ref> The victim is unable to perform complex tasks with the hands; the hands become numb. Blood vessels in the outer extremities constrict, lessening heat loss to the outside air. Breathing becomes quick and shallow. [[Goose bumps]] form, raising body hair on end in an attempt to create an [[Thermal insulation|insulating]] layer of air around the body (which is of limited use in humans due to lack of sufficient hair, but useful in other species). Often, a person will experience a warm sensation, as if they have recovered, but they are in fact heading into Stage 2. Another test to see if the person is entering stage 2 is if they are unable to touch their thumb with their little finger; this is the first stage of muscles not working. In stage 2, body temperature drops by 2-4°C. Shivering becomes more violent. Muscle mis-coordination becomes apparent.<ref name=sterba/><ref name=francis/><ref name=cheung>{{cite journal |author=Cheung SS, Montie DL, White MD, Behm D |title=Changes in manual dexterity following short-term hand and forearm immersion in 10 degrees C water |journal=Aviat Space Environ Med |volume=74 |issue=9 |pages=990–3 |year=2003 |month=September |pmid=14503680 |doi= |url=http://www.ingentaconnect.com/content/asma/asem/2003/00000074/00000009/art00013 |accessdate=2008-06-11}}</ref> Movements are slow and labored, accompanied by a stumbling pace and mild confusion, although the victim may appear alert. Surface blood vessels contract further as the body focuses its remaining resources on keeping the vital organs warm. The victim becomes pale. Lips, ears, fingers and toes may become blue. In stage 3, body temperature drops below approximately {{Convert|32|°C|°F|1|lk=on}}. Shivering usually stops.<ref name=sterba/><ref name=francis/> Difficulty speaking, sluggish thinking, and amnesia starts to appear; inability to use hands and stumbling is also usually present. Cellular metabolic processes shut down. Below {{Convert|30|°C|°F|1|lk=on}}, the exposed skin becomes blue and puffy, muscle coordination becomes very poor, walking becomes almost impossible, and the victim exhibits incoherent/irrational behavior including [[terminal burrowing]] or even a [[stupor]]. [[Pulse]] and [[Respiration (physiology)|respiration]] rates decrease significantly but fast heart rates (ventricular tachycardia, atrial fibrillation) can occur. Major organs fail. [[Clinical death]] occurs. Because of decreased cellular activity in stage 3 hypothermia, the body will actually take longer to undergo [[brain death]]. === Immersion Hypothermia === Hypothermia of both the extremities and body core continues to be a major limitation to [[Underwater diving|diving]] in cold water.<ref name=sterba/> Cooling in the extremities is often the limitation to operations.<ref name=sterba/> The fingers decrease dexterity due to pain or numbness, safety, work capacity, and increase the risk of developing nonfreezing cold injury.<ref name=sterba/><ref name=cheung/> In divers breathing [[heliox]] below 100 meters wearing [[Diving suit|hot water suits]], the inspired gas must be heated or the symptoms of hypothermia can set in without the divers realizing it.<ref name=sterba/> Other predisposing factors leading to immersion hypothermia include [[dehydration]], inadequate rewarming with [[Dive_profile#Repetitive_diving|repetitive operations]], starting operations while cold, wet [[dry suit]] undergarments, [[Perspiration|sweating]] with work, inadequate [[thermal insulation]] (for example, thin dry suit undergarment), lack of heated breathing gas with deep heliox diving, and poor [[Physical exercise|physical conditioning]].<ref name=sterba/> == Treatments == Treatment for hypothermia consists of drying, sheltering, and gradually warming (making sure to not rub the patient's body, to warm with blankets and, if possible, to transfer your own body heat). While [[blankets]] help a person retain body heat, they are not sufficient to treat hypothermia. It is vital that you warm the core of the body first or the cold blood will be forced towards the heart and may cause death. In the field, a mildly hypothermic person can be effectively rewarmed through close body contact from a companion and by drinking warm, sweet liquids. Moderate and severe cases of hypothermia require immediate evacuation and treatment in a hospital. In hospital, warming is accomplished by external techniques such as heated blankets for mild hypothermia and by more invasive techniques such as warm fluids injected in the veins or even [[lavage]] (washing) of the bladder, stomach, chest and abdominal cavities with warmed fluids for severely hypothermic patients.{{Fact|date=February 2007}} 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 accounts of recovery after prolonged cardiac arrest have been reported in patients with hypothermia.{{Fact|date=April 2008}} 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 == Appropriate clothing helps to prevent hypothermia. Wearing [[cotton]] in cool weather is a particular hypothermia risk as it retains [[water]], and water rapidly conducts heat away from the body. Even in dry weather, cotton clothing can become damp from perspiration, and chilly after the wearer stops exercising. [[Synthetic fabric|Synthetic]] and [[wool]] fabrics provide far better insulation when wet and are quicker to dry. Some synthetic fabrics are designed to wick perspiration away from the body. In air, most heat (20 to 40 percent) is lost through the head; covering the head and neck is quite important in reducing the likelihood of hypothermia.<ref>{{cite web |author=University of Oklahoma, Health Science Center |title=Environmental Stress Program, Heat and Cold Stress |year=2001 |url=http://w3.ouhsc.edu/ehso/HeatColdStress.pdf |accessdate=2008-06-18}}</ref><ref>{{cite web |author=The Merck Manuals |title=Cold injury |year=2005 |url=http://www.merck.com/mmpe/sec21/ch319/ch319a.html |accessdate=2008-06-18}}</ref><ref>{{cite web |author=Macnair, T |publisher=BBC Health |title=Hypothermia |url=http://www.bbc.co.uk/health/conditions/hypothermia1.shtml#how_can_it_be_prevented? |accessdate=2008-06-18}}</ref> Heat loss on land is very difficult to predict due to multiple variables such as clothing type and quantity, amount of insulating fat on the victim, environmental humidity or personal dampness such as after exertion, the circumstances surrounding the hypothermic episode, and so on. Heat is lost much faster in water, hence the need for [[wetsuit]]s or [[drysuit]]s in cold-weather activities such as [[kayaking]].<ref name=sterba/> Water temperatures that would be quite reasonable as outdoor air temperatures can lead to hypothermia very quickly. For example, a water temperature of 10 degrees Celsius (50 F) can be expected to lead to death in approximately 1 hour, and water temperatures hovering at freezing can lead to death in as little as 15 minutes. <ref>{{cite web|url=http://www.usps.org/national/ensign/uspscompass/compassarchive/compassv1n1/hypothermia.htm|accessdate=2008-02-19|title=Hypothermia safety|publisher=[[United States Power Squadrons]]|date=January 23, 2007}}</ref> But in water, even a temperature as high as 26 degrees celcius (80 F) may, eventually (after many hours) lead to mild hypothermia. <ref>{{cite web |author=Dawson, CP |title=Hypothermia Prevention: Survival in Cold Water |publisher=Minnesota Sea Grant |year=1987 |url=http://www.seagrant.umn.edu/coastal_communities/hypothermia |accessdate=2008-06-18}}</ref> Alcohol consumption prior to cold exposure may increase one's risk of becoming hypothermic. Alcohol acts as a [[vasodilator]], increasing blood flow to the body's extremities, thereby increasing heat loss.<ref>{{cite web |url=http://www.bbc.co.uk/health/conditions/hypothermia1.shtml |title=Hypothermia |author=Hicks, R |date=January 2007 |publisher=BBC Health |accessdate=2008-02-19}}</ref> Ironically, this may cause the victim to ''feel'' warm while he or she is rapidly losing heat to the surrounding environment. The [[United States Coast Guard]] promotes using life vests as a method of prevention against hypothermia through the 50/50/50 rule: if someone is in 50-degree water for 50 minutes they have a 50 percent better chance of survival if they are wearing a life jacket.<ref>{{cite web |author=United States Coast Guard |title=Recreational Boating Safety Information |url=http://www.uscg.mil/d13/units/grupangeles/BoatSafe.htm |publisher=United States Coast Guard |accessdate=2008-06-18}}</ref> ==Benefits== There is considerable evidence that children who suffer near-[[drowning]] accidents in water near 0°C (273 K) can be revived over an hour after losing consciousness<ref>{{cite journal | author=Bolte RG, Black PG, Bowers RS, Thorne JK, Corneli HM | title=The use of extracorporeal rewarming in a child submerged for 66 minutes | journal=''[[Journal of the American Medical Association]]'' | volume=260 | issue=3 | year=1988 | pages=377–379 | pmid=3379747 | doi=10.1001/jama.260.3.377 }}</ref>. The cold water considerably lowers [[metabolism]], allowing the brain to withstand a much longer period of [[Hypoxia (medical)|hypoxia]]. == Therapeutic hypothermia == {{main|therapeutic hypothermia}} == Paradoxical undressing == 20% to 50% of hypothermal deaths are associated with a phenomenon known as paradoxical undressing. This typically occurs during moderate to severe hypothermia as the victim becomes disoriented, confused, and combative. The hypothermic victim may begin discarding the clothing he or she has been wearing, which in turn increases the rate of temperature loss.<ref>{{cite journal |title=The word: Paradoxical undressing - being-human |year=2007 |author=New Scientist |journal=New Scientist |url=http://www.newscientist.com/channel/being-human/mg19426002.600-the-word-paradoxical-undressing.html |accessdate=2008-06-18}}</ref> There have been several published case studies of victims throwing off their clothes before help reached them.<ref name="pmid541627">{{cite journal |author=Wedin B, Vanggaard L, Hirvonen J |title="Paradoxical undressing" in fatal hypothermia |journal=J. Forensic Sci. |volume=24 |issue=3 |pages=543–53 |year=1979 |month=July |pmid=541627 |doi= |url= }}</ref> Rescuers who are trained in mountain survival techniques have been taught to expect this effect. However, the phenomenon still regularly leads police to assume incorrectly that urban victims of hypothermia have been subjected to a sexual assault. {{Fact|date=June 2007}} One explanation for the effect is a cold-induced malfunction of the [[hypothalamus]], the part of the brain that regulates body temperature. Another explanation is that the muscles contracting peripheral blood vessels become exhausted (known as a loss of vasomoter tone) and relax, leading to a sudden surge of blood (and heat) to the extremities, fooling the victim into feeling warm. == See also == * [[Hyperthermia]] * [[Cryonics]] * [[Therapeutic hypothermia]] * [[Wilderness first aid]] * [[Frostbite]] * [[Heat escape lessening position]] * [[Hibernation]] * [[Torpor]] * [[Thermoregulation]] * [[Wilson's syndrome]] * [[Nazi human experimentation]] ==References== <!-- ---------------------------------------------------------- See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for a discussion of different citation methods and how to generate footnotes using the <ref>, </ref> and <reference /> tags ----------------------------------------------------------- --> {{reflist|2}} ==External links== * [http://www.sarbc.org/hypo.html Search and Rescue Society of British Columbia internet site (SARBC.ORG) (hypothermia division)] * [http://www.theberries.ns.ca/Archives/Hypothermia2.html Hypothermia] * http://www.hypothermia.org/ * [http://www.msc.ec.gc.ca/education/windchill/windchill_chart_e.cfm Windchill chart in km/h windspeeds and °C temperature measures] * [http://www.wildernessutah.com/brain/hypothermia.html Wilderness Utah - Treating Hypothermia in the Wilderness] * [http://www.helptheaged.org.uk/CampaignsNews/Poverty/WinterDeaths/default.htm Help the Aged charity (United Kingdom) - hypothermia in the elderly] * [http://symptoms.wrongdiagnosis.com/cosymptoms/cold-hands/hypothermia-desc.htm Cold hands and Hypothermia] {{Consequences of external causes}} [[Category:Diving medicine]] [[Category:Medical emergencies]] [[Category:Physiology]] [[Category:Causes of death]] [[Category:Cryobiology]] [[cs:Podchlazení]] [[da:Hypotermi]] [[de:Hypothermie]] [[el:Υποθερμία]] [[es:Hipotermia]] [[fr:Hypothermie]] [[it:Ipotermia]] [[he:קור (תסמין למחלה)]] [[nl:Hypothermie]] [[ja:低体温症]] [[no:Hypotermi]] [[pl:Hipotermia]] [[pt:Hipotermia]] [[fi:Hypotermia]] [[sv:Hypotermi]] [[vi:Hypothermia]] [[uk:Гіпотермія]]