Recognize symptoms of hypothermia and treat it fast.
Hypothermia occurs when the body’s normal temperature (around 98.6 F – 95.0 F) drops significantly to lower levels. Recognizing hypothermia is fairly easy if you know the signs to look for. Hypothermia is a condition in which core temperature drops below that required for normal metabolism and body functions which is defined as 35.0 °C (95.0 °F). As body temperature decreases, characteristic symptoms occur such as shivering and mental confusion.
Recognize symptoms of hypothermia and treat it fast
Hypothermia is the opposite of hyperthermia which is present in heat exhaustion and heat stroke. Hypothermia describes a state in which the body’s mechanism for temperature regulation is overwhelmed in the face of a cold stressor. Hypothermia is classified as accidental or intentional, primary or secondary, and by the degree of hypothermia.
- Intentional hypothermia is an induced state generally directed at neuroprotection after an at-risk situation.
- Primary hypothermia is due to environmental exposure, with no underlying medical condition causing disruption of temperature regulation.
- Secondary hypothermia is low body temperature resulting from a medical illness lowering the temperature set-point.
What causes and the mechanisms of Hypothermia
Hypothermia can happen from accidental exposure to cold, to immersion in cold water, or to trauma from a serious accident. Wearing wet clothes can raise your risk of hypothermia. Elderly people are especially susceptible. Hypothermia may develop over hours or days if your body can’ t regulate heat as it should, if you can’ t sense how cold it is, or if you live in a cold environment in the winter. Diseases of the endocrine glands may also cause your body to have trouble producing heat.
The body maintains a stable core temperature through balancing heat production and heat loss. At rest, humans produce 40-60 kilocalories (kcal) of heat per square meter of body surface area through generation by cellular metabolism, most prominently in the liver and the heart. Heat production increases with striated muscle contraction; shivering increases the rate of heat production 2-5 times.
Heat loss occurs via several mechanisms, the most significant of which, under dry conditions, is radiation (55-65% of heat loss). Conduction and convection account for about 15% of additional heat loss, and respiration and evaporation account for the remainder. Conductive and convective heat loss, or direct transfer of heat to another object or circulating air, respectively, are the most common causes of accidental hypothermia.
The hypothalamus controls thermoregulation via increased heat conservation (peripheral vasoconstriction and behavior responses) and heat production (shivering and increasing levels of thyroxine and epinephrine). The mechanisms for heat preservation may be overwhelmed in the face of cold stress and core temperature can drop secondary to fatigue or glycogen depletion.
Hypothermia affects virtually all organ systems. Hypothermia results in decreased depolarization of cardiac pacemaker cells, causing bradycardia. Mean arterial pressure and cardiac output decrease, and an electrocardiogram (ECG) may show characteristic J or Osborne waves.
Many patients have recovered from severe hypothermia, so early recognition and prompt initiation of optimal treatment is paramount.
Other cold-related injuries that can either be present alone or in combination with hypothermia include:
- Chilblains are superficial ulcers of the skin that occur when a predisposed individual is repeatedly exposed to cold.
- Frostbite involves the freezing and destruction of tissue.
- Frostnip is a superficial cooling of tissues without cellular destruction.
- Trench foot or immersion foot is due to repetitive exposure to wet, non-freezing temperatures.
Signs and Symptoms of hypothermia:
Blood pressure and heart rate increase. Muscles tense and shiver; this produces more body heat, but results in a loss of dexterity and motor control. As your body’s core temperature drops further, blood pressure, pulse, and respiration rates all decrease.
As conditions worsen, your mental attitude and level of consciousness change. Resisting help and acting irrational or confused are common indicators of hypothermia. As your core temperature drops dangerously low, you become semiconscious, then unconscious. Stress, shock, and low core temperatures may cause cardiac and respiratory failure.
- Skin that is cold to the touch
- Shivering at first, then the absence of shivering
- Lethargy, drowsiness
- Weakness, clumsiness
- Irritability, combativeness
- Confusion, delirium, hallucinations
- Slow reflexes
- Seizure, stupor, or coma
- Slowed, shallow, or arrested breathing
- Slowed, irregular, or arrested heartbeat
How to Prevent Hypothermia
Appropriate clothing helps to prevent hypothermia. Synthetic and wool fabrics are superior to cotton as they provide better insulation when wet and dry. Some synthetic fabrics, such as polypropylene and polyester, are used in clothing designed to wick perspiration away from the body, such as liner socks and moisture-wicking undergarments.
The United States Coast Guard promotes using life vests as a method of protection against hypothermia through the 50/50/50 rule: If someone is in 50 °F (10 °C) water for 50 minutes, he/she has a 50 percent better chance of survival if wearing a life jacket.
- Cover. Wear a hat or other protective covering to prevent body heat from escaping from your head, face and neck. Cover your hands with mittens instead of gloves. Mittens are more effective than gloves because mittens keep your fingers in closer contact with one another.
- Overexertion. Avoid activities that would cause you to sweat a lot. The combination of wet clothing and cold weather can cause you to lose body heat more quickly.
- Layers. Wear loosefitting, layered, lightweight clothing. Outer clothing made of tightly woven, water-repellent material is best for wind protection. Wool, silk or polypropylene inner layers hold body heat better than cotton does.
- Dry. Stay as dry as possible. Get out of wet clothing as soon as possible. Be especially careful to keep your hands and feet dry, as it’s easy for snow to get into mittens and boots.
Nutritional tips may help reduce symptoms of cold exposure:
- Eat warming spices in your foods, such as basil, ginger, turmeric, garlic, and cayenne.
- Eat more hot soups made with fresh vegetables.
- Avoid coffee and other stimulants, alcohol, and especially tobacco. Tobacco causes blood vessels to constrict and may increase risk to hypothermia.
- Drink 6 – 8 glasses of filtered water daily. Hydration is important in reducing problems from cold exposure.
According to one study, overall in-patient mortality in hypothermic patients was 12%. Most people tolerate mild hypothermia (32-35°C body temperature) fairly well, which is not associated with significant morbidity or mortality. In contrast, a multicenter survey found a 21% mortality rate for patients with moderate hypothermia (28-32°C body temperature). Mortality is even higher in severe hypothermia (core temperature below 28°C). Despite hospital-based treatment, mortality from moderate or severe hypothermia approaches 40%.
“Indoor hypothermia” is more likely to occur in patients with significant medical comorbidities (alcoholism, sepsis, hypothyroidism/hypopituitarism) and tends to carry worse outcomes than exposure hypothermia. According to current records, approximately 700 people die in the United States from accidental primary hypothermia each year.
