Signs and Symptoms of Hypothermia

The signs and symptoms of hypothermia are divided roughly by the severity of the hypothermia. There isn't a universal definition of the categories of severity, but most healthcare providers use mild, moderate, and severe, defined by body temperature and associated signs.

Cold exposure can come on slowly, affecting someone before he or she realizes there's a problem. If you're not looking for the signs and symptoms of hypothermia, it can be easy to miss until the problem has become significant.

Suspicion of hypothermia is almost as important as recognizing the signs and symptoms. It's just as important to recognize the conditions under which hypothermia can happen and pay close attention to the people exposed to those conditions, including yourself.

Mild Hypothermia

As the body cools, it will take steps to prevent the heat loss. The earliest signs of hypothermia occur when skin temperature (not core body temperature) falls below an average of about 95 degrees when measured over several areas of the body—what's known as the mean skin temperature.

At this early stage, circulation to the skin is decreased, which keeps blood away from the cold surface of the body and helps to preserve core body temperature. The person might notice that fine motor skills (texting on a phone, for example) are getting harder to perform and they are beginning to shiver. Shivering comes from the body expending energy to create heat and is a coping mechanism for cold exposure.

Actual hypothermia occurs when the core body temperature falls below 95 degrees. Uncontrollable shivering is the first and most obvious sign of mild hypothermia.

If you are removed or protected from the cold environment (e.g. with blankets, dry clothes, hot cocoa), mild hypothermia can be reversed fairly easily. If not, the core body temperature is likely to continue to drop.

Moderate/Severe Hypothermia

If left untreated, mild hypothermia could worsen and body temperature could drop below 90 degrees and becomes moderate hypothermia. Shivering stops as the body switches from using energy as a source of heat to conserving energy in the face of cold exposure.

Once you become moderately hypothermic, the situation must be addressed, or you will continue to worsen and will develop severe hypothermia.

As the core body temperature drops below 83 degrees, you will most likely be unconscious and unresponsive to most stimuli. Often, deep tendon reflexes are diminished or absent, meaning that you will not respond to any attempts to be woken up.

Patients with this stage of hypothermia are at an increased risk for sudden cardiac arrest due to the irritability of heart muscle tissues at lower temperatures. Even rewarming will require close monitoring in the event that the patient suffers a cardiac arrhythmia.

Complications

Elderly patients, very young patients, patients with diabetes or circulatory problems, and patients with low body fat are more susceptible to hypothermia and its complications compared to the rest of the population.

Frostbite

In freezing temperatures, the body's response to hypothermia also creates an increased risk for frostbite. Frostbite occurs when body tissues freeze and crystallize. The most distal parts of the body are most susceptible to frostbite (fingers, toes, nose, and earlobes). This is where it is hardest to flood tissues with a constant flow of warm blood.

In cold environments, the first compensatory mechanism a person's body will use to reduce heat loss is to shunt blood away from the body's surface. This has the undesirable effect of not warming those distal points. Freezing environmental temperatures will cause freezing in tissues without fresh, warm blood to counteract it.

It is possible to develop frostbite without developing hypothermia, but the presence of frostbite is an indicator that the environment is dangerously cold and hypothermia is possible.

When to See a Doctor

The mildest hypothermia can be treated without any help from a healthcare provider. Simply moving the patient to a warm, dry environment will usually do the trick.

While waiting for an ambulance, if possible, move the patient to a dry, warm environment. Remove any wet clothes. A dry patient with a thin blanket is better than a patient covered in multiple layers of wet clothing.