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Frostbite and Hypothermia Symptoms and Stages

Medical Author: Benjamin C. Wedro, MD, FACEP, FAAEM
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

Frostbite and hypothermia are the consequences of cold exposure and both can have long lasting effects.

Not all organs in the body are created equal. While the body tries to maintain a constant temperature where heat production is balanced by heat loss, it is quite willing to sacrifice expendable parts like fingers and toes to protect vital organs like the heart and brain. When exposed to a cold environment, the body tries to keep blood circulating away from the skin where it can be cooled by the outside weather. Shivering starts to generate heat and can compensate well if the cold exposure is short-lived. If, however, the body remains in the cold, bad things can happen very quickly.

What is paradoxical undressing?

Interestingly, there is a phenomenon called paradoxical undressing, in which the cold person actually undresses instead of trying to bundle up. It is not uncommon for the hypothermic victim to just curl up in a snow bank and die. The heart also does strange things when it gets cold. A normal heart rhythm can become irritable and eventually degenerate into ventricular fibrillation where the bottom chambers of the heart jiggle like a bowl of Jell-O. This lack of electrical impulse doesn't allow the heart to beat and pump blood to the body and is one of the causes of sudden cardiac death.

What are the symptoms and stages of frostbite?

The stages of frostbite are similar to those of burns.

  • Frostnip or first degree frostbite is superficial and reversible but may cause significant pain when the extremity rewarms.
  • Second degree frostbite is characterized by blisters that form a few hours to a day after injury and signifies deeper tissue damage.
  • Third degree frostbite describes skin that has been damaged though all its layers and tissue that turns black and hard as it dies.
  • Fourth degree frostbite occurs when bone and tendon freeze.

It may take many days for the depth of frostbite to cause symptoms and the amount of damage to the tissue may not be known.

Cold is a dangerous element, so don't let hypothermia catch you!

Picture of the stages of frostbitePicture of the stages of frostbite

What are the risk factors for frostbite and hypothermia?

Alcohol consumption is an important risk factor for getting frostbite and hypothermia. Aside from impairing judgment, it may cause blood vessels in the skin to dilate, sending blood to the body's surface where it is exposed to the cold weather causing just the opposite effect of what the body wants to do to, which is preserve heat. Alcohol also makes shivering less effective, decreasing heat production.

With decreased blood supply to the skin, the far reaches of the body's circulation are at risk for damage. Fingers, toes, ears, and nose are the first parts of the body to be at risk for frostbite. Without adequate blood supply to provide internal heat, water in the tissue can form small ice crystals and the first signs of frostbite begin. The skin may become cold, numb, and hard. The hands or feet can become clumsy and after a time, the skin can blister.

What is hypothermia?

The electrical conducting systems of the brain and heart are very sensitive to decreasing core body temperatures and start to fail as the body cools. Hypothermia is defined as a body temperature less than 95 F (35 C), and signs and symptoms of mild hypothermia are lethargy and confusion. The colder the body gets, the more confused the person gets, and decision making begins to suffer. Instead of coming out of the cold, apathy sets in and the patient may become delirious.

What are the symptoms of hypothermia?

Symptoms of hypothermia include:

  • Initial hunger and nausea will give way to apathy as the core body temperature drops.
  • This is followed by confusion, lethargy, slurred speech, loss of consciousness, and coma.
  • Often the affected person will lie down, fall asleep, and die. In some cases, the patient will paradoxically remove their clothes just before this occurs.

The decrease in brain function occurs in direct relationship to the decrease in body temperature (the colder the body, the less the brain function). Brain function stops at a core temperature of 68 F (20 C).

The heart is subject to abnormal electrical rhythms as hypothermia progresses. Ventricular fibrillation, a disorganized rhythm in which the heart is unable to pump, may occur at core temperatures below 82.4 F (28 C). This is one type of cardiac arrest. This is important to recognize since this irritability and risk of sudden cardiac death also may occur when the body is rewarmed.

REFERENCE: Auerbach P. Wilderness Medicine. 6th edition. United States. Mosby 2011

Last Editorial Review: 1/6/2014

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