How Cold Is Too Cold?

January has arrived and brought with it the frigid temperatures of a New England winter. Daily temperatures rarely exceed the thirties during this time of year and can often be as cold as the teens with nights even falling below zero. Add in a wind chill and the air can be downright dangerous to human beings. But how cold is too cold for the body to endure? WebMD reports that somewhere between 700 and 1,500 people die from cold-weather exposure annually in the U.S. Cold-weather injuries are divided into hypothermia, freezing-tissue injuries and non-freezing injuries by medical professionals. It's important to know that the body can lose heat in several different ways. Evaporation is the loss of heat through sweating and respiration and totals about 15 to 25 percent of heat loss. Radiation, the most common at 50 to 65 percent, is similar to a woodstove; the body emits thermal radiation to its cooler surroundings. Thirdly, conduction is the loss of heat through contact with a cold surface, such as water or snow; and lastly, convection is loss of heat through air movement across the skin. These two together total about 15 percent of heat loss, although that number can increase with environmental factors such as wind speed, precipitation and clothing. Hypothermia is the drop in core body temperature from the norm of about 98.6 degrees Fahrenheit to below 95 degrees. In severe hypothermia, the core body temperature drops to below 82 degrees. This body temperature drop can happen rapidly, within a few hours, or slowly over several days or even weeks. In addition to duration of time, many environmental conditions can lead to hypothermia: cold temperatures, inadequate clothing, moisture, nutrition deficiencies and exposed skin. The highest-risk groups for developing hypothermia are the elderly, infants and children, the unhoused and cold-weather athletes. Other risk factors include certain medical conditions (diabetes, thyroid conditions, etc.), certain medications, emotional distress or drug and alcohol use. The initial warning signs of hypothermia are feeling cold, shivering, confusion, weak pulse and a loss of motor function. Early symptoms of hypothermia should be treated immediately to prevent the continuation of the core's temperature drop. First aid treatment for hypothermia incudes removal of wet clothes/hats/footwear, covering with warm clothes and blankets, providing shelter from the elements and rewarming the body with extra clothing/blankets and warm liquids (not alcohol or caffeine). Advanced states of hypothermia may require hospital treatment to rewarm the core. Severe symptoms can be slurred speech, intense shivering, coordination difficulties and irrational behaviors. Hypothermia can negatively impact many of the body's critical systems, such as the nervous system, cardiovascular system, respiratory system and renal system, leading to death if not treated immediately. Medical treatment for hypothermia can involve passive warming with blankets and warm drinks, blood rewarming with a hemodialysis machine, providing warm intravenous fluids, airway rewarming with humidified oxygen or irrigation of the lung area and abdominal cavity with a warm saltwater solution by catheter. Another dangerous freezing injury is frostbite, which occurs when body tissue freezes. Frostbite occurs in phases that range from frostnip and mild frostbite to deep frostbite. The first stage starts when the skin cools below 50 degrees, becoming cold and red. Frostnip feels like a tingling, painful sensation and is most common in the nose, ears, cheeks, fingers, and toes. It causes no long-term damage. Mild frostbite is when skin temperature drops below 28 degrees and tissues freeze, first appearing red and then white or pale. It can sting, burn, and swell, as well as develop into a blister after rewarming. Deep frostbite affects deep layers of the skin, causing a white or blue-gray coloring and numbness, as well as large blisters post-rewarming. It can have a black and hard appearance as the tissue dies, called gangrene. Frostbite requires immediate medical attention. The affected area should be gently rewarmed (do not rub) with clothing or coverings. Lack of attention to frostbitten areas can result in gangrene and may require amputation. One example of a nonfreezing cold injury is chilblains, or small, itchy bumps on the skin as a reaction to cold temperatures, like a rash. These red bumps can be tender, itchy and painful but can be treated by covering with dry and warm clothing. Hypothermia can generally be prevented in everyday situations through awareness and following safety measures. Know the temperature before heading outdoors and dress warmly in multiple layers with head and hand coverings to avoid heat loss. Do not drink alcohol or caffeine in cold weather as they can cool the blood. Avoid excessive sweating as wet clothing combined with cold weather will also accelerate heat loss. Children and the elderly should be monitored for appropriate outerwear and layers, as well as brought inside immediately and warmed if they begin to shiver. Confirm that elderly relatives and neighbors have an adequate heat source in their homes and are dressed warmly, even when indoors. Taking the appropriate precautions to prevent cold-weather injuries can ensure that time spent outdoors in a New England winter doesn't take a dangerous turn.