Hypothermia: Symptoms, treatment, and stages

Hypothermia happens when the body temperature falls below a safe level, and it can be fatal. Infants and older people are especially at risk.

Under healthy conditions, the body maintains a relatively stable temperature of around 98.6˚F or 37˚C.

If the environment gets too cold or the body is unable to produce sufficient heat, the core temperature can drop, and hypothermia can develop.

Between 2003 and 2013, more than 13,400 people died from hypothermia in the United States, according to the Centers for Disease Control and Prevention (CDC).

What is hypothermia?

People stranded in car in cold.
Hypothermia happens when the body cannot produce enough energy to keep warm. Older people and children are especially susceptible.

Hypothermia is a severe condition in which the body temperature drops to an abnormally low level. It occurs when the body is unable to produce enough heat to counter the heat that it is losing.

The part of the brain that controls body temperature is called the hypothalamus. When the hypothalamus recognizes changes in body temperature, it initiates body responses to bring the temperature back in line.

The body produces heat during routine metabolic processes in cells that support vital bodily functions. Most heat leaves the body through the skin’s surface by the processes of convection, conduction, radiation, and evaporation.

If the environment becomes colder, the body shivers. This increase in muscle activity generates more heat. However, if the body loses heat more quickly than it can make it, the core temperature will fall.

As the temperature falls, the body shunts blood away from the skin to reduce the amount of heat that escapes.

Instead, it directs blood flow to the vital organs of the body, such as the heart, lungs, kidney, and brain. The heart and brain are most sensitive to lower temperatures, and electrical activity in these organs slows down when they become cold.

If the body temperature keeps falling, the organs begin to fail, ultimately leading to death.

Hypothermia is the opposite of hyperthermia, which involves an elevated body temperature and can present as heat exhaustion or heat stroke.

Symptoms

A person can become disoriented.
A person can become disoriented and may not take action to get warm.

As hypothermia sets in, it becomes more challenging to think, move, and take preventive action. This is dangerous because it means that people who have hypothermia will not seek to keep themselves warm and safe.

The body starts to slow down as the temperature drops. If the person stops shivering, it can be a sign that their condition is getting worse.

The individual is at risk of lying down, falling asleep, and dying. In some cases, people will paradoxically remove their clothes just before this occurs.

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Treatment

Treatment depends on the degree of hypothermia, but the aim will be to make the person warm.

Treatments include the following:

First aid treatment

Anyone with symptoms of hypothermia will need immediate medical assistance.

Until medical assistance arrives, taking the following action can help:

moving the person to a warm, dry place, if possible, or sheltering them from the elements

removing wet clothing, cutting items away if necessary

covering their whole body and head with blankets, leaving only the face clear

putting the individual on a blanket to insulate them from the ground

monitoring breathing and carrying out CPR if breathing stops

providing skin-to-skin contact, if possible, by removing clothing and wrapping yourself and the individual in the blanket together to transfer heat

providing warm drinks, if the individual is conscious, but no alcohol or caffeine

It is vital not to use direct heat, such as heat lamps or hot water, as this can damage the skin. It can also trigger irregular heartbeats and, potentially, lead to cardiac arrest.

Do not rub or massage the person either, as these potentially jarring movements could also cause cardiac arrest.

Clinical treatment

According to an article published in the American Family Physician (AFP), the journal of the American Academy of Family Physicians (AAFP), the following techniques can help treat hypothermia.

Passive external rewarming: This uses the individual’s heat-generating ability. It involves removing their cold, wet clothing, ideally replacing it with adequately insulated, dry clothing, and moving them to a warm environment.

Active external rewarming: This involves applying warming devices, such as hot-water bottles or warmed forced air, externally to truncal areas of the body. For example, the individual could hold a hot-water bottle under each arm.

Active core rewarming: This uses warmed, intravenous fluids to irrigate body cavities, including the thorax, peritoneum, stomach, and bladder. Other options include getting the individual to inhale warm, humidified air, or applying extracorporeal rewarming by using a heart-lung machine.

Do not give a person alcohol if they have signs of hypothermia, and avoid giving any drinks to an unconscious person.

A person with severe hypothermia may not seem to have a pulse or be breathing. If they appear to be dead, the CDC advise bystanders to give CPR while keeping the person warm and waiting for emergency help. It is possible that this may resuscitate them.

Stages

Hypothermia generally progresses in three stages from mild to moderate and then severe.

According to the AAFP, the signs and symptoms of these stages are as follows:

Stage Body temperature Signs and symptoms
Mild 90°F to 95°F (32.2°C to 35°C) High blood pressure, shivering, rapid breathing and heart rate, constricted blood vessels, apathy and fatigue, impaired judgment, and lack of coordination.
Moderate 82.4°F to 90°F (28°C to 32.2°C) Irregular heartbeat, a slower heart rate and breathing, lower level of consciousness, dilated pupils, low blood pressure, and a decrease in reflexes.
Severe Less than 82.4°F (28°C) Labored breathing, nonreactive pupils, heart failure, pulmonary edema, and cardiac arrest.

Additional symptoms of hypothermia may include:

Mild:

dizziness

hunger and nausea

difficulty speaking

Moderate to severe:

shivering may stop

slurred speech

significant confusion

drowsiness

apathy or lack of concern

weak pulse

When a person has severe hypothermia, they may no longer know what they are doing, due to a change in mental consciousness.

Paradoxical undressing

Back in 1979, researchers described a phenomenon known as paradoxical undressing.

In paradoxical undressing, people remove their clothes despite the cold. As a result of doing this, they lose more body heat, which can be fatal. This can happen during the later stages of hypothermia as the person becomes disoriented, confused, and possibly combative.

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