hypothermia
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Hypothermia
Definition
Hypothermia, a potentially fatal condition, occurs when body temperature falls below 95°F (35°C).
Description
Although hypothermia is an obvious danger for people living in cold climates, many cases have occurred when the air temperature is well above the freezing mark. Elderly people, for instance, have succumbed to hypothermia after prolonged exposure to indoor air temperatures of 50-65°F (10-18.3°C). In the United States, hypothermia is primarily an urban phenomenon associated with alcoholism, drug addiction, mental illness, and cold—water immersion accidents. The victims are often homeless male alcoholics. Officially, 11,817 deaths were attributed to hypothermia in the United States from 1979 to 1994, but experts suspect that many fatal cases go unrecognized. Nearly half the victims were 65 or older, with males dominating every age group. Nonwhites were also overrepresented in the statistics. Among males 65 and older, nonwhites outnumbered whites by more than four to one.
Causes and symptoms
Measured orally, a healthy person's body temperature can fluctuate between 97°F (36.1°C) and 100°F (37.8°C). Survival depends on maintaining temperature stability within this range by balancing the heat produced by metabolism with the heat lost to the environment through (for the most part) the skin and lungs. When environmental or other changes cause heat loss to outpace heat production, the brain triggers physiological and behavioral responses to restore the balance. The involuntary muscular activity of shivering, for example, aids heat production by accelerating metabolism. But if the cold stress is too great and the body's defenses are overwhelmed, body temperature begins to fall. Hypothermia is considered to begin once body temperature reaches 95°F (35°C), though even smaller drops in temperature can have an adverse effect.
Hypothermia is divided into two types: primary and secondary. Primary hypothermia occurs when the body's heat-balancing mechanisms are working properly but are subjected to extreme cold, whereas secondary hypothermia affects people whose heat-balancing mechanisms are impaired in some way and cannot respond adequately to moderate or perhaps even mild cold. Primary hypothermia typically involves exposure to cold air or immersion in cold water. The cold air variety usually takes at least several hours to develop, but immersion hypothermia will occur within about an hour of entering the water, since water draws heat away from the body much faster than air does. In secondary hypothermia, the body's heat-balancing mechanisms can fail for any number of reasons, including strokes, diabetes, malnutrition, bacterial infection, thyroid disease, spinal cord injuries (which prevent the brain from receiving crucial temperature-related information from other parts of the body), and the use of medications and other substances that affect the brain or spinal cord. Alcohol is one such substance. In smaller amounts it can put people at risk by interfering with their ability to recognize and avoid cold-weather dangers. In larger amounts it shuts down the body's heat-balancing mechanisms.
Secondary hypothermia is often a threat to the elderly, who may be on medications or suffering from illnesses that affect their ability to conserve heat. Malnutrition and immobility can also put the elderly at risk. Some medical research suggests as well that shivering and blood vessel narrowing—two of the body's defenses against cold—may not be triggered as quickly in older people. For these and other reasons, the elderly can, over a period of days or even weeks, fall victim to hypothermia in poorly insulated homes or other surroundings that family, friends, and caregivers may not recognize as life threatening. Another risk for the elderly is the fact that hypothermia can easily be misdiagnosed as a stroke or some other common illness of old age.
The signs and symptoms of hypothermia follow a typical course, though the body temperatures at which they occur vary from person to person depending on age, health, and other factors. The impact of hypothermia on the nervous system often becomes apparent quite early. Coordination, for instance, may begin to suffer as soon as body temperature reaches 95°F (35°C). The early signs of hypothermia also include cold and pale skin and intense shivering; the latter stops between 90°F (32.2°C) and 86°F (30°C). As body temperature continues to fall, speech becomes slurred, the muscles go rigid, and the victim becomes disoriented and experiences eyesight problems. Other harmful consequences include dehydration as well as liver and kidney failure. Heart rate, respiratory rate, and blood pressure rise during the first stages of hypothermia, but fall once the 90°F (32.2°C) mark is passed. Below 86°F (30°C) most victims are comatose, and below 82°F (27.8°C) the heart's rhythm becomes dangerously disordered. Yet even at very low body temperatures, people can survive for several hours and be successfully revived, though they may appear to be dead.
Diagnosis
Information on the patient's prior health and activities often helps doctors establish a correct diagnosis and treatment plan. Pulse, blood pressure, temperature, and respiration require immediate monitoring. Because the temperature of the mouth is not an accurate guide to the body's core temperature, readings are taken at one or two other sites, usually the ear, rectum, or esophagus. Other diagnostic tools include electrocardiography, which is used to evaluate heart rhythm, and blood and urine tests, which provide several kinds of key information; a chest x ray is also required. A computed tomography scan (CT scan) or magnetic resonance imaging (MRI) may be needed to check for head and other injuries.
Treatment
Emergency medical help should be summoned whenever a person appears hypothermic. The danger signs include intense shivering; stiffness and numbness in the arms and legs; stumbling and clumsiness; sleepiness, confusion, disorientation, amnesia, and irrational behavior; and difficulty speaking. Until emergency help arrives, a victim of outdoor hypothermia should be brought to shelter and warmed by removing wet clothing and footwear, drying the skin, and wrapping him or her in warm blankets or a sleeping bag. Gentle handling is necessary when moving the victim to avoid disturbing the heart. Rubbing the skin or giving the victim alcohol can be harmful, though warm drinks such as clear soup and tea are recommended for those who can swallow. Anyone who aids a victim of hypothermia should also look for signs of frostbite and be aware that attempting to rewarm a frostbitten area of the body before emergency help arrives can be extremely dangerous. For this reason, frostbitten areas must be kept away from heat sources such as campfires and car heaters.
Rewarming is the essence of hospital treatment for hypothermia. How rewarming proceeds depends on the body temperature. Different approaches are used for patients who are mildly hypothermic (the patient's body temperature is 90-95 °F [32.2-35 °C]), moderately hypothermic (86-90 °F [30-32.2 °C]), or severely hypothermic (less than 86 °F [30 °C]). Other considerations, such as the patient's age or the condition of the heart, can also influence treatment choices.
Mild hypothermia is reversed with passive rewarming. This technique relies on the patient's own metabolism to rewarm the body. Once wet clothing is removed and the skin is dried, the patient is covered with blankets and placed in a warm room. The goal is to raise the patient's temperature by 0.5-2 °C an hour.
Moderate hypothermia is often treated first with active external rewarming and then with passive rewarming. Active external rewarming involves applying heat to the skin, for instance by placing the patient in a warm bath or wrapping the patient in electric heating blankets.
Severe hypothermia requires active internal rewarming, which is recommended for some cases of moderate hypothermia as well. There are several types of active internal rewarming. Cardiopulmonary bypass, in which the patient's blood is circulated through a rewarming device and then returned to the body, is considered the best, and can raise body temperature by 1-2 °C every 3-5 minutes. However, many hospitals are not equipped to offer this treatment. The alternative is to introduce warm oxygen or fluids into the body.
Hypothermia treatment can also include, among other things, insulin, antibiotics, and fluid replacement therapy. When the heart has stopped, both cardiopulmonary resuscitation (CPR) and rewarming are necessary. Once a patient's condition has stabilized, he or she may need treatment for an underlying problem such as alcoholism or thyroid disease.
Prognosis
Victims of mild or moderate hypothermia usually enjoy a complete recovery. In regard to severely hypothermic patients, the prognosis for survival varies due to differences in people's physiological responses to cold.
Key terms
Antibiotics — Substances used against microorganisms that cause infection.
Computed tomography — A process that uses x rays to create three-dimensional images of structures inside the body.
Esophagus — A muscular tube through which food and liquids pass on their way to the stomach.
Insulin — A substance that regulates blood glucose levels. Glucose is a sugar.
Magnetic resonance imaging — The use of electromagnetic energy to create images of structures inside the body.
Metabolism — The chemical changes by which the body breaks down food and other substances and builds new substances necessary for life.
Nervous system — The system that transmits information, in the form of electrochemical impulses, throughout the body. It comprises the brain, spinal cord, and nerves.
Rectum — The lower section of the large intestine. The intestines are part of the digestive system.
Stroke — A condition involving loss of blood flow to the brain.
Thyroid — A gland (fluid-secreting structure) in the neck. It plays an important role in metabolism.
Prevention
People who spend time outdoors in cold weather can reduce heat loss by wearing their clothing loosely and in layers and by keeping their hands, feet, and head well covered (30-50% of body heat is lost through the head). Because water draws heat away from the body so easily, staying dry is important, and wet clothing and footwear should be replaced as quickly as possible. Wind- and water-resistant outer garments are also crucial. Alcohol should be avoided because it promotes heat loss by expanding the blood vessels that carry body heat to the skin.
Preventing hypothermia among the elderly requires vigilance on the part of family, friends, and caregivers. An elderly person's home should be properly insulated and heated, with living areas kept at a temperature of 70 °F (21.1 °C). Warm clothing and bedding are essential, as are adequate food, rest, and exercise; warming the bed and bedroom before going to sleep is also recommended. Older people who live alone should be visited regularly—at least once a day during very cold weather—to ensure that their health remains sound and that they are taking good care of themselves. For help and advice, family members and others can turn to government and social service agencies. Meals on wheels and visiting nurse programs, for instance, may be available, and it may be possible to obtain financial aid for winterizing and heating homes.
Resources
Books
Petty, Kevin J. "Hypothermia." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
hypothermia
[hi″po-ther´me-ah]low body temperature; it may be symptomatic of a disease or disorder of the temperature-regulating mechanism of the body, may be due to exposure to cold, or may be induced for certain surgical procedures or as a therapeutic measure. Hypothermia is a nursing diagnosis accepted by the North American Nursing Diagnosis Association, defined as body temperature reduced below the normal range for an individual but not below 35.6°C rectally (36.4°C rectally for the newborn). adj., adj hypother´mal, hypother´�mic.
Emergency treatment for hypothermia includes administration of warm intravenous fluid and use of esophageal rewarming tubes and special rewarming blankets. Resuscitation efforts such as cardiopulmonary resuscitation should continue until the patient is warmed to a normal core temperature; if there is no other change, the patient may be pronounced dead.
Emergency treatment for hypothermia includes administration of warm intravenous fluid and use of esophageal rewarming tubes and special rewarming blankets. Resuscitation efforts such as cardiopulmonary resuscitation should continue until the patient is warmed to a normal core temperature; if there is no other change, the patient may be pronounced dead.
accidental hypothermia unintended lowering of body heat due to prolonged exposure to cold. Hypothermia is a chilling of the entire body, but the extremities can withstand temperatures as much as 10 to 15°C (20 to 30°F) lower than the torso, where vital organs are located. When the core temperature drops even a few degrees, physiologic changes can lead to fatal cardiac arrhythmias and respiratory failure. Persons most at risk for accidental hypothermia include the very young, the very thin, the very old, the mentally challenged or emotionally unstable, alcohol and drug abusers, and the homeless. Symptoms range from mild shivering and complaints of feeling chilled to loss of consciousness, absence of reflexes, and barely detectable pulse and respirations.
Prevention and Treatment. Accidental hypothermia can be avoided by eating high-energy foods, exercising when in the cold, wearing layers of clothing, and covering the head. From one half to two thirds of the body heat is lost through the head. For persons on a fixed or limited income, suggestions for avoiding hypothermia in a cold home must be realistic. Blankets and quilted covers that snap together to form a snug bag are alternatives to turning up the thermostat. A loose knitted cap worn day and night can help reduce loss of body heat. Persons who live alone may need help in finding another individual or agency that can check on them daily when the outside temperatures are very low.
The diagnosis of hypothermia may be missed if a clinical thermometer such as the kind used to measure fever is employed to determine the core temperature of a potential hypothermia victim. These thermometers rarely register temperatures below 34.5°C (94.1°F), while the patient's actual temperature can be as low as 30°C (86°F). Emergency departments should be equipped with special monitoring equipment that gives a true picture of the body temperature.
Once hypothermia is diagnosed, rewarming is indicated. Outside a medical facility the rewarming should be gradual so as to avoid respiratory and cardiac problems associated with rapidly sending cold blood back to the heart. The torso is warmed first by wrapping it in warm blankets or submersion in a tepid bath. Once the core temperature reaches 35°C (95°F), the extremities are warmed.
The diagnosis of hypothermia may be missed if a clinical thermometer such as the kind used to measure fever is employed to determine the core temperature of a potential hypothermia victim. These thermometers rarely register temperatures below 34.5°C (94.1°F), while the patient's actual temperature can be as low as 30°C (86°F). Emergency departments should be equipped with special monitoring equipment that gives a true picture of the body temperature.
Once hypothermia is diagnosed, rewarming is indicated. Outside a medical facility the rewarming should be gradual so as to avoid respiratory and cardiac problems associated with rapidly sending cold blood back to the heart. The torso is warmed first by wrapping it in warm blankets or submersion in a tepid bath. Once the core temperature reaches 35°C (95°F), the extremities are warmed.
environmental hypothermia accidental hypothermia due to heat loss due to a combination of convection, conduction, and radiation to the surrounding ambient air.
induced hypothermia deliberate reduction of the temperature of all or part of the body; sometimes used as an adjunct to anesthesia in surgical procedures involving a limb, and as a protective measure in cardiac and neurologic surgery. The hypothermia may be continued only for the duration of the operation or it may be prolonged for as long as 5 days, depending on the reason for its use. See also hypothermia treatment.
Local Hypothermia. This is a type of refrigeration anesthesia restricted to a part of the body, such as a limb. It usually is used to produce surgical anesthesia immediately before amputation. Advantages include minimal risk of shock, lowering of cell metabolism, and elimination of the need for inhalation anesthesia in patients who are poor surgical risks. The part to be anesthetized is packed in ice or wrapped in a special refrigeration unit consisting of coiled tubes. Tourniquets are applied to the limb to inhibit circulation and avoid general chilling of the patient. The limb is chilled for 3 to 5 hours before amputation.
General Hypothermia. Generalized lowering of the body temperature decreases the metabolism of tissues and thereby the need for oxygen; it is used in various surgical procedures, especially on the heart. The core temperature is maintained between 26°C and 32°C (78.8°F and 89.6°F).
To induce general hypothermia, the patient is wrapped in a cooling blanket containing coils through which cold water or an antifreeze, or both, are circulated. The fastest method for achieving hypothermia is extracorporeal cooling of the blood; the patient's blood is removed through a cannula inserted in a large vessel, circulated through refrigerated coils and returned via another cannulated vessel.
Rewarming of the patient is accomplished simply by removing cooling blankets and allowing the temperature to rise gradually and naturally. In most cases regular blankets are used to maintain body warmth. External heat in the form of hot water bottles or warm tub baths, if used at all, must be applied with extreme caution to avoid burning the patient.
To induce general hypothermia, the patient is wrapped in a cooling blanket containing coils through which cold water or an antifreeze, or both, are circulated. The fastest method for achieving hypothermia is extracorporeal cooling of the blood; the patient's blood is removed through a cannula inserted in a large vessel, circulated through refrigerated coils and returned via another cannulated vessel.
Rewarming of the patient is accomplished simply by removing cooling blankets and allowing the temperature to rise gradually and naturally. In most cases regular blankets are used to maintain body warmth. External heat in the form of hot water bottles or warm tub baths, if used at all, must be applied with extreme caution to avoid burning the patient.
Patient Care. During hypothermia and the rewarming process the patient's temperature, pulse, respiration, and blood pressure must be checked frequently. Special electronic thermometers are often used so that the body temperature can be monitored at all times. In prolonged hypothermia, cardiac irregularities or respiratory difficulties may develop quickly; the patient must be watched constantly for changes in the vital signs, and any changes must be reported immediately. The skin also should be observed for signs of developing pressure ulcers, edema, or marked discoloration.
The patient should be turned at least every 2 hours, with special attention to proper positioning and good body alignment. Decreased secretion of saliva and mouth-breathing demand frequent mouth care. The eyes may need to be irrigated frequently and covered with compresses moistened with physiologic saline solution or artificial tears if the corneal reflex is diminished and eye secretions are reduced.
Intake and output are measured and recorded. An indwelling catheter is inserted prior to induction of hypothermia and is left in place until normal body temperature is established. This is necessary because urinary output is diminished during hypothermia. Fluids are given intravenously and the oral intake of food and liquids is prohibited because of depression of the gag reflex.
Shivering during prolonged hypothermia must be avoided as it tends to elevate the body temperature and increase metabolic needs, thereby defeating the purpose of hypothermia.
During the rewarming process the patient must be observed for signs of increased tendency to bleed and of gastric distention; these are common complications. After the body temperature returns to normal and becomes stabilized, the patient is allowed to progress to a normal diet and physical activities.
The patient should be turned at least every 2 hours, with special attention to proper positioning and good body alignment. Decreased secretion of saliva and mouth-breathing demand frequent mouth care. The eyes may need to be irrigated frequently and covered with compresses moistened with physiologic saline solution or artificial tears if the corneal reflex is diminished and eye secretions are reduced.
Intake and output are measured and recorded. An indwelling catheter is inserted prior to induction of hypothermia and is left in place until normal body temperature is established. This is necessary because urinary output is diminished during hypothermia. Fluids are given intravenously and the oral intake of food and liquids is prohibited because of depression of the gag reflex.
Shivering during prolonged hypothermia must be avoided as it tends to elevate the body temperature and increase metabolic needs, thereby defeating the purpose of hypothermia.
During the rewarming process the patient must be observed for signs of increased tendency to bleed and of gastric distention; these are common complications. After the body temperature returns to normal and becomes stabilized, the patient is allowed to progress to a normal diet and physical activities.
moderate hypothermia body temperature of 23° to 32°C, resulting from surface cooling.
profound hypothermia body temperature of 12° to 20°C.
regional hypothermia temperature reduction in a limb or organ resulting from application of external cold or perfusion with a cold solution.
symptomatic hypothermia pathologic reduction of body temperature as a result of decreased heat production or increased heat loss. Hypothyroidism, severe blood loss with circulatory failure, and damage to the heat-producing cells of the hypothalamus can lead to decreased heat production. Prolonged exposure to cold, overdosage of antipyretic drugs, such as aspirin, and profuse sweating (diaphoresis) are some causes of increased heat loss and resultant hypothermia.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
hy·po·ther·mi·a
(hī'pō-ther'mē-ă),A body temperature significantly less than 98.6°F (37°C).
[hypo- + G. thermē, heat]
Farlex Partner Medical Dictionary © Farlex 2012
hypothermia
(hī′pə-thûr′mē-ə)n.
Abnormally low body temperature.
hy′po·ther′mic (-mĭk) adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
hypothermia
Critical care A ↓ in core/rectal body temperature ≤ 35ºC–95ºF, due to long-term occupational or recreational exposure to ↓ air or water temperatures Epidemiology Hypothermia causes 750 deaths/yr; racial differences in mortality 3.2–white vs 13.1–blacks deaths/106 ♂; 1.4 vs 4.1 deaths/106–♀–US Clinical ↓ Respiratory rate, metabolic acidosis, ↓ pulse, ↓ blood pressure, ventricular fibrillation, hypo- or hyperglycemia, coagulopathy, hemoconcentration, pneumonia, renal failure, pancreatitis; when extreme and prolonged, drowsiness, delirium, coma, shivering, numbness, fatigue, poor coordination, slurred speech, impaired mentation, blue and/or puffy skin, irrational thinking Risk factors Extremes of age–related to ↓ shivering mechanisms, less protective fat, ↓ mobility, ↓ metabolic rate, and chronic illness, alcohol use/abuse, use of neuroleptic agents, hypothyroidism, mental illness, starvation, dehydration, poverty, immobilizing illness, and young adults in winter sports Treatment External rewarming, best performed in a warm tub at 40-42ºC–104-107.6ºF; internal rewarming is recommended for those with severe hypothemia and includes extracorporeal blood warming using a femorofemoral bypass and/or repeated peritoneal dialysis with 2 L of warmed–43ºC K+-free dialysate solution. See Accidental hypothermia Neurology The intentional cooling Pts with traumatic brain injury and 'salvageable' Glasgow coma scores–5 to 7 on admission to 33º for 24 hrs is associated with an improved survival–62% good outcomes in the hypothermia group vs 38% good outcomes in the normothermia group Mechanism Hypothermia ↓ 2º brain injury by an unknown mechanism, possibly by ↓ brain metabolism, ↓ extracellular concentrations of excitatory neurotransmitters–eg, glutamate, ↓ post-traumatic inflammatory response, with ↓cytokine release.McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
hy·po·ther·mi·a
(hī'pō-thĕr'mē-ă)A core body temperature significantly lower than 98.6°F (37°C).
[hypo- + G. thermē, heat]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
hypothermia
Below-normal body temperature. This may occur, especially in the elderly, as a result of prolonged exposure to low temperatures or may be brought about deliberately to reduce tissue oxygen requirements during surgery, especially HEART SURGERY.Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
hypothermia
an abnormally low body temperature that reduces the metabolic rate to a dangerous level and can lead to death, often occurring in elderly people subjected to cold weather. Hypothermia is sometimes induced in medical treatment in order to reduce metabolic activity.Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
hy·po·ther·mi·a
(hī'pō-thĕr'mē-ă)A body temperature significantly less than 98.6°F (37°C).
[hypo- + G. thermē, heat]
Medical Dictionary for the Dental Professions © Farlex 2012
Patient discussion about hypothermia
Q. what is the red line when your body temperature drops before you are getting hypothermia?
A. Hypothermia is a condition in which an organism's temperature drops below that required for normal metabolism and function. For people in stage 1 hypethermia, body temperature drops by 1-2°C below normal temperature (35-36°C). Mild to strong shivering occurs. In stage 2, body temperature drops by 2-4°C (35-33 degrees). Shivering becomes more violent. Muscle mis-coordination becomes apparent and movements are slow and labored and there is mild confusuin. In stage 3, body temperature drops below approximately 32 °C (89.6 °F). Shivering usually stops and there's difficulty speaking, sluggish thinking, and amnesia start to appear. Cellular metabolic processes shut down. This is life threatening.
Q. what can be done for spontaneous hypothermia? is there a deficiency of hormones or anything that can be taken
A. hypothermia can be caused by al sort of things. Some bacterial infections, poisoning, aciduria , hypothyroidism and more. Is this the only symptom? I’m sure there are some others. But I think this could be a good idea to check up with a Dr.
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