Hypothermia

Hypothermia is a medical condition where the human body core temperature drops below 95°F (35°C). Under normal circumstances, the body maintains a steady temperature through a process called thermoregulation. This internal system manages heat production and heat loss to keep the body stable. When this system fails, the body loses heat faster than it can generate it. The name itself comes from the Greek words "ypo," meaning under, and "therme," meaning heat.

There are several ways the body can lose heat or fail to produce it. Classically, hypothermia occurs through exposure to cold weather or immersion in cold water. Heat is lost much faster in water than in the air. For instance, water at 50°F can kill an adult in only one hour. Water near freezing can be fatal in as little as 15 minutes. During the sinking of the Titanic, most people in the water died within 15 to 30 minutes. Other causes include conditions that decrease heat production, such as low blood sugar (hypoglycemia), anorexia, or advanced age. Alcohol intoxication is also a major risk factor. Alcohol causes vasodilation, which is the widening of blood vessels. This increases blood flow to the skin, making a person feel warm while they are actually losing heat. Alcohol also interferes with the brain's ability to shiver and regulate temperature.

Medical professionals use different systems to classify the severity of hypothermia. The Swiss staging system focuses on the symptoms a person shows when a core temperature cannot be measured. In Stage 1, or mild hypothermia, the person is awake and shivering. Stage 2, or moderate hypothermia, involves the person becoming drowsy and shivering stops. Stage 3, or severe hypothermia, is characterized by the person being unconscious and not shivering. Finally, Stage 4 is profound hypothermia, where the person has no vital signs.

Symptoms change significantly as the body temperature drops. In the mild stage, the sympathetic nervous system becomes excited. This leads to shivering, high blood pressure, a fast heart rate, and a fast respiratory rate. A person might also experience mental confusion or increased urine production. As the condition reaches the moderate stage, symptoms include amnesia, slurred speech, and a loss of fine motor skills. In the severe stage, the body's physiological systems begin to fail. The heart rate and blood pressure decrease significantly. At a temperature of 82°F, a person's heart rate may drop into the 30s. The person may also experience hallucinations or fixed, dilated pupils.

During severe stages, the brain may exhibit strange and dangerous behaviors. One phenomenon is called paradoxical undressing. This occurs in 20% to 50% of hypothermia deaths. As the person becomes disoriented, they may begin removing their clothing. This might happen because the hypothalamus, the brain's temperature control center, malfunctions. Alternatively, the muscles controlling blood vessels may become exhausted and relax. This causes a sudden surge of warm blood to the skin, making the victim feel overheated. Another behavior is terminal burrowing, or "hide-and-die syndrome." This is an apparent self-protective behavior where the person enters small, enclosed spaces like under a bed.

Treating hypothermia depends on how severe the drop in temperature is. For mild cases, doctors recommend warm drinks, warm clothing, and voluntary physical activity. Moderate cases may require heating blankets or warmed intravenous (IV) fluids. For severe cases, medical teams may use extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass. These machines help oxygenate the blood outside the body. If a person has no pulse, doctors perform cardiopulmonary resuscitation (CPR). Rewarming is usually continued until the person's temperature rises above 95°F. However, if there is no improvement or if blood potassium levels exceed 12 millimoles per litre, resuscitation may be stopped.

Hypothermia has a significant impact on human history and modern health. In the United States, it causes at least 1,500 deaths every year. It is more common among males and older populations. History shows that cold has also played a major role in many wars.

Even in accidental cases, survival is possible. One documented case involved a two-year-old boy in Poland named Adam, who survived accidental hypothermia. In cases where ECMO or bypass is used, the survival rate is around 50%. Understanding these processes helps rescuers and doctors save lives in both urban and wilderness environments.