Hypothermia

Definition:
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....click & see

Hypothermia is the opposite of hyperthermia, the condition which causes heat exhaustion and heat stroke.

Hypothermia occurs when the body’s core temperature is lowered due to exposure to cold. It can occur even at mild temperatures if exposure is prolonged.

The body’s natural defences against the cold consist of restricting the flow of blood to the skin so as to prevent heat loss, along with shivering and releasing hormones to generate heat.

These measures are limited and are usually inadequate to maintain body temperature in cold environments.

Causes:
The causes vary, and include increased susceptibility to flu and other viruses.
However, hypothermia is one of the most deadly cold-induced conditions and, if not caught and treated early on, can lead to a rapid decline in the body’s ability to function normally.

Unlike other warm-blooded animals that have a layer of fur or blubber to keep them warm, you need an extra layer of clothing to keep you warm when it’s cold outside. Without that extra layer of clothing, more heat escapes from your body than your body can produce. If too much heat escapes, the result is hypothermia. Exposure to cold water and certain medical conditions also can cause hypothermia.

Your normal core body temperature is usually right around 98.6 F. In hypothermia, your body fails to maintain a normal temperature. An internal body temperature of 95 F or lower signals hypothermia.

The cause of hypothermia usually is extended exposure to cold temperatures or a cool, damp environment. Other contributing causes include inadequate clothing and neglecting to adequately cover your extremities, particularly your head — a disproportionate amount of heat is lost through your head.

Hypothermia in milder weather

Hypothermia can happen not just in cold winter weather, when there are low temperatures or low wind chill factors, but under milder conditions as well. A rain shower that soaks you to the skin on a cool day can lead to hypothermia if you don’t move inside to warm up and dry off. If you stay outside, evaporation of the water from your skin further cools your body, lowering your internal temperature. A wind blowing over the wet parts of your body greatly increases evaporation and cooling.

An accidental fall into cold water is especially likely to lead to hypothermia. Hypothermia may develop within minutes of being exposed to cold water, or it may take several hours, depending on the water temperature. Water doesn’t have to be icy cold to cause hypothermia. Your body loses heat more quickly in water than in air. Any water temperature lower than your body temperature causes your body to lose at least some heat.

Click to see:->How We Lose Heat to the Environment

Symptoms:
Symptoms take effect in three stages.

Normal body temperature in humans is 37°C.

The first stage – mild hypothermia – is characterised by:

* Bouts of shivering;
* Grogginess and muddled thinking.

In stage 1, body temperature drops by 1-2°C below normal temperature (35-38°C). Mild to strong shivering occurs.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 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.

Indicators of moderate hypothermia are:

* Violent shivering or shivering which suddenly stops;
* Inability to think and pay attention;
* Slow, shallow breathing;
* Slow, weak pulse.

In stage 2, body temperature drops by 2-4°C. Shivering becomes more violent. Muscle mis-coordination becomes apparent. 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.

Severe hypothermia has set in when:

* Shivering stops;
* The patient loses consciousness;
* There is little or no breathing;
* Pulse is weak, irregular or non-existent.

In stage 3, body temperature drops below approximately 32 °C (89.6 °F). Shivering usually stops.[1][2] 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 30 °C (86.0 °F), 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 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 diving in cold water. Cooling in the extremities is often the limitation to operations. The fingers decrease dexterity due to pain or numbness, safety, work capacity, and increase the risk of developing nonfreezing cold injury.

In divers breathing heliox below 100 meters wearing hot water suits, the inspired gas must be heated or the symptoms of hypothermia can set in without the divers realizing it.

Other predisposing factors leading to immersion hypothermia include dehydration, inadequate rewarming with repetitive operations, starting operations while cold, wet dry suit undergarments, sweating with work, inadequate thermal insulation (ex. thin dry suit undergarment), lack of heated breathing gas with deep heliox diving, and poor physical conditioning.

Risk factors:
Being in extreme cold, wearing wet clothes — especially in the presence of wind — and being in cold water can all play a part in increasing your chances of hypothermia. In addition, other factors make you more vulnerable:

* Advanced age. People age 65 and older are especially vulnerable because they may have other illnesses or take medications that can interfere with the body’s ability to regulate temperature.
* Very young age. Children usually lose heat faster than adults do. Children have a larger head-to-body ratio than adults do, making them more prone to heat loss through the head. Children may also ignore the cold because they’re having too much fun to think about it. And they may not have the judgment to dress properly in cold weather or to get out of the cold when they feel cold. Infants may have a special problem with the cold because they have less efficient mechanisms for generating heat.
* Mental impairment. People with Alzheimer’s disease or another illness that causes mental impairment may not be aware of the risks of being out in the cold. Wandering is not uncommon among people with Alzheimer’s, and some affected people may stray away from home and be unable to find their way back on their own. Being stranded leaves them vulnerable to the weather.
* Alcohol and drug use. Alcohol may make your body feel warm inside, but it lowers your body’s ability to retain heat. Both alcohol and drugs such as marijuana can keep your blood vessels dilated, restrict your shivering response, impair your judgment and alter your awareness of weather conditions.
* Certain medical conditions. Some health disorders affect your body’s ability to respond to cold or to produce heat. Examples include untreated underactive thyroid (hypothyroidism), stroke, severe arthritis, Parkinson’s disease, trauma, spinal cord injuries, burns, blood vessel or nerve disorders that affect sensation in your extremities (for example, peripheral neuropathy in people with diabetes), dehydration and any condition that limits activity or restrains the normal flow of blood. Older adults are more likely to have one or more of these risk factors.
* Water conditions. Factors contributing to your risk of hypothermia in cold water include the temperature of the water and the length of time you spend in it. Rescue time is crucial when a person accidentally falls into cold water. Chances of survival are affected by how cold the water is: The colder the water, the less the chance of survival.

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Treatment:
The first step is to contact the emergency services as extreme hypothermia requires urgent professional attention.

All cold, wet clothing should be replaced with warm, dry clothing to prevent further heat loss immediately.

If breathing has stopped or there is no pulse, cardiopulmonary resuscitation (CPR) should be attempted until the emergency services arrive.

Rapid rewarming with hot water or massaging cold extremities should be avoided as, if done improperly, it could lead to serious tissue damage.

Do not give alcohol or nicotine products to someone suffering from hypothermia.

Complications:
Complications depend on how low your body temperature falls. If you’re in water, you may lose consciousness and drown before your temperature drops low enough to cause death by hypothermia. Other complications of hypothermia may include:

* Frostbite
* Loss of limbs
* Coma

The lower your core body temperature, the greater your chance of complications and permanent damage.

 

First aid to Hypothermia patient…...click & see

.Prevention:
The key rules are to wear many layers of clothing, drink plenty of fluids and hot drinks (but not alcohol) and keep well nourished.

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 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.

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 etc. Heat is lost much faster in water, hence the need for wetsuits or drysuits in cold-weather activities such as kayaking. 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. But in water, even a temperature as high as 80 degrees Fahrenheit may eventually lead to hypothermia.

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. 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

Maintaining movement to keep circulation up is also advised.

Age Concern advises keeping at least one room well-heated during the winter months.

Is help available?
Age Concern runs a Be a Good Neighbour scheme during winter.

The scheme calls on people to be aware of elderly people living nearby and to help out with routine tasks.

Dr Simon Fradd, of the Doctor Patient Partnership, said: “Helping collect prescriptions, getting prescriptions or just making time for a chat are a few simple ways we can help.”

More details can be obtained from Age Concern’s freephone line on 0800 00 99 66.
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. The cold water considerably lowers metabolism, allowing the brain to withstand a much longer period of hypoxia.

Medically induced
Induced hypothermia (also known as therapeutic hypothermia) is the intentional induction of hypothermia for medical purposes. Such practice has been shown to reduce brain damage in infants and increase survivability in certain cases of cardiac arrest. The method also has applications in cardiac surgery and stroke recovery.
Hypothermia being induced by using water circulated through heat-conducting pads

.
Hypothermia may be a consequence of anesthetic induction 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, allowing blood to flow 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 the hypothalamus is also affected by drugs causing the normal temperature control limits to be increased, compromising the body’s normal cold response system.

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. There have been several published case studies of victims throwing off their clothes before help reached them.

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.[citation needed]

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.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.

Resources:
http://news.bbc.co.uk/2/hi/health/medical_notes/276284.stm
http://en.wikipedia.org/wiki/Hypothermia
http://www.mayoclinic.com/health/hypothermia/

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