Hypothermia is a dangerous condition defined by a significant drop in the body’s core temperature below the normal threshold of 98.6°F (37°C). It is clinically recognized as a medical emergency when the internal temperature falls below 95°F (35°C). This occurs when the body loses heat faster than it can produce it, causing thermoregulation mechanisms to fail. Untreated hypothermia impairs the nervous system, slows organ function, and can lead to heart and respiratory failure.
Defining the Stages of Hypothermia
Hypothermia is classified into mild, moderate, and severe stages based on core body temperature and corresponding symptoms. Mild hypothermia is characterized by a core temperature between 95°F and 89.6°F (35°C and 32°C). At this stage, the body attempts to generate heat through vigorous, uncontrollable shivering, which is the body’s primary defense mechanism. Other noticeable symptoms include slurred speech, confusion, and a lack of coordination, making simple tasks difficult.
In the moderate range, between 89.6°F and 82.4°F (32°C and 28°C), the body’s response changes dramatically. Shivering typically stops in this stage because the body’s metabolic reserves become depleted, which is a deceptive and dangerous sign. The person’s mental state declines significantly, often presenting as increasing confusion, amnesia, and a decreased level of consciousness. Heart rate, breathing, and blood pressure all begin to slow down as the circulatory system attempts to conserve heat by limiting blood flow to the extremities.
Severe hypothermia occurs below 82.4°F (28°C), a life-threatening state where consciousness is usually lost. The body becomes rigid, and the pulse and respiratory rate become extremely slow and weak, sometimes making them difficult for an untrained person to detect. At this profound temperature, the risk of lethal cardiac events, specifically ventricular fibrillation, increases dramatically. The body’s systems are shutting down, and immediate medical intervention is necessary for survival.
Immediate Emergency Response
Upon suspecting hypothermia, contact emergency medical services immediately. While waiting for professional help, the priority is to prevent further heat loss and initiate passive external rewarming gently. This process begins with moving the individual out of the cold environment, such as indoors or into a sheltered area, and insulating them from the cold ground with a blanket or pad.
It is important to remove any wet clothing, as water conducts heat away from the body 25 times faster than air, replacing it with dry clothes or blankets. The focus of warming should be on the core—the chest, neck, head, and groin—rather than the extremities. If the person is conscious and able to swallow, offer warm, non-alcoholic, non-caffeinated beverages to help raise the internal temperature slightly and provide energy.
Avoid actions that could worsen the condition or trigger a cardiac event. Do not attempt to warm the person rapidly with direct heat sources like heating lamps or hot baths. Aggressive rewarming of the arms and legs should also be avoided. This can cause cold, acidic blood from the limbs to rush back to the core, leading to a dangerous drop in core temperature known as “afterdrop,” which may induce an irregular heart rhythm. Finally, avoid giving the person alcohol, as it causes peripheral blood vessels to dilate and accelerates heat loss.
Factors Increasing Vulnerability
Certain demographic groups and underlying health conditions increase susceptibility to hypothermia, even in moderately cool environments. Both the very young and the elderly are at heightened risk because their bodies have less efficient temperature regulation mechanisms. Infants lose heat more rapidly due to their large surface area relative to their body mass and may not have the energy reserves to shiver effectively.
Underlying medical conditions can impair the body’s ability to produce or conserve heat. These include hypothyroidism and diabetes, which affect metabolism and blood flow. Conditions causing poor circulation, such as cardiovascular disease, also limit the body’s ability to shunt warm blood to the core effectively. Substance abuse, particularly alcohol and recreational drugs, is a major risk factor. It impairs judgment, leading to prolonged exposure, and causes blood vessels to dilate, accelerating heat loss.
Certain medications, such as neuroleptics and beta-blockers, can interfere with the body’s natural thermoregulatory response to cold. Malnutrition and exhaustion deplete the energy reserves necessary for the body to generate heat through shivering and metabolic activity. Individuals with mental health conditions or dementia may also be vulnerable because their impaired judgment can prevent them from seeking shelter or dressing appropriately for the weather.