Hypothermia

Hypothermia occurs when the body temperature drops below what is necessary to sustain metabolism and activity (for humans, below 35 °C). A cold environment, prolonged exposure, rain, wind, sweating, or being in cold water can induce hypothermia.

The normal human body temperature is about 37 °C. Hypothermia progresses through three stages.

First Stage of Hypothermia

In the first stage, the body temperature drops 1–2 °C below normal. The person experiences mild to severe shivering, hands become numb, and complex actions with them become difficult. Limb blood vessels constrict, reducing heat loss. Additional symptoms include rapid and shallow breathing and goosebumps (though the effect is minimal in humans). Often, the person may start feeling warmth—a misleading sensation indicating a transition to the second stage. The inability to pinch the thumb and little finger also manifests.

Second Stage of Hypothermia

During the second stage, the body temperature drops 2–4 °C. Shivering intensifies, lack of muscle coordination becomes visible, movements slow and require great effort, and unsteady gait and mild confusion occur. Although the victim may appear alert, surface blood vessels further contract to preserve heat for vital organs. The nose, lips, ears, fingers, and toes may turn blue.

Third Stage of Hypothermia

In the third stage, the body temperature drops below 32 °C. Shivering usually subsides; speaking becomes difficult, slow thinking and memory impairment (amnesia) occur, and the inability to use hands and stumbling frequently appear. Cellular metabolic processes stop. When the temperature drops below 30 °C, exposed skin turns blue, swells, muscle coordination deteriorates significantly, walking becomes nearly impossible, and irrational behavior such as hiding in small enclosed spaces becomes evident. Pulse and breathing slow significantly, but heart rate may increase. As vital organs cease functioning, clinical death occurs, with brain death following later due to slowed cell activity.

Preventing Hypothermia

Proper clothing helps prevent hypothermia. Cotton clothes pose the greatest risk as they retain water and accelerate heat loss. In dry weather, cotton clothes can become wet from sweat and later cool down. Damp synthetic and woolen fabrics provide better insulation and dry faster, some of them also absorb sweat. Covering the head and neck reduces the risk, as a large portion of body heat (20–40%) escapes through the head.

Assessing the rate of heat loss in dry conditions is challenging due to factors such as type and quantity of clothing, insulating layer of body fat, and environmental humidity. Heat loss in water occurs much faster than in air, necessitating wetsuits for cold water activities.

Risk Factors

Alcohol consumption before entering a cold environment increases the risk of hypothermia, as alcohol enhances blood flow to the extremities, promoting heat loss despite feeling warm. Elderly and sick individuals are more prone to hypothermia in cold conditions, and infants also face higher risk due to underdeveloped temperature self-regulation mechanisms.

Paradoxical Undressing

In 20–50% of hypothermia victims, “paradoxical undressing” occurs. This phenomenon is typical for moderate to severe hypothermia, where the victim experiences disorientation, perceives heat, and undresses, thereby increasing heat loss from the body.