Hypothermia is a medical emergency caused by prolonged exposure to very cold temperatures and the body loses heat faster than it can produce it. Normal body temperature is about 98.6°F/37°C. When body temperatures drop below 95°F/35°C it is considered hypothermia.
The onset of hypothermia can occur slowly and it can affect the brain, so many people who have hypothermia are not aware of it.
How long it takes to die from hypothermia depends on several factors, including whether the cold exposure is in air or water, how cold the temperatures are, and the person’s underlying health and age. Depending on the conditions, hypothermia can occur within minutes to hours, or slowly over days to weeks.
In the air, hypothermia can develop in as little as five minutes in temperatures of minus -50°F/-45.5°C in people who are not dressed properly and have exposed skin. At -30°F/-34.4°C, hypothermia can occur in about 10 minutes. Death can occur in under an hour in extremely cold conditions.
People die of hypothermia faster in water than in air, because water has a high thermal conductivity that can cool a person at least 24-times faster than air.
A person who is immersed in near-freezing water at temperatures of 32.5°F/0.3°C will have symptoms of mild hypothermia in under 2 minutes and will be unconscious in less than 15 minutes, with an expected survival time of 15 to 45 minutes.
What Are Symptoms of Hypothermia?
Symptoms of mild hypothermia (body temperature of 90° to 95°F/32° to 35°C) include:
- Bluish skin
- Trouble speaking clearly
- Memory problems
- Altered judgment
- Breathing faster than usual (hyperventilation)
- Loss of balance or coordination/clumsiness
- Fast heart rate
- Urinating more than usual
Symptoms of moderate hypothermia (body temperature of 82° to 90°F/28° to 32°C) include:
- Shivering stops
- Feeling very tired
- Seeing things that are not there (hallucinations)
- Shallow breathing
- Decreased reflexes
- Paradoxical undressing (undressing despite the need for clothing to keep warm)
- Increased risk for abnormal heartbeats (arrhythmias)
- Dilated pupils
Symptoms of severe hypothermia (body temperature less than 82°F/28°C) include:
- Low blood pressure
- Muscle rigidity
- Passing out
- Breathing stops
- Heart stops
Symptoms of hypothermia in babies may also include:
- Bright red, cold skin
- Very low energy
What Causes Hypothermia?
Hypothermia is caused by prolonged exposure to extremely cold temperatures.
Risk factors for developing hypothermia include:
- Babies and young children
- Adults over 50 with low or high body mass
- Certain medical conditions
- Addison’s disease
- Kidney disease
- Conditions that impair body temperature regulation (thermoregulation)
- Central nervous system (CNS) trauma
- Toxicologic and metabolic derangements
- Intracranial bleeding
- Parkinson’s disease
- Brain or spinal cord tumors
- Wernicke disease
- Multiple sclerosis
- Use of certain medications
- Diabetes medications
- Blood pressure medications
- General anesthetics
- Past frostbite or hypothermia
- Drinking too much alcohol or taking recreational drugs
- Elevated blood alcohol levels and combinations of alcohol and recreational drug can also cause hypothermia on their own
How Is Hypothermia Diagnosed?
In addition to a patient history and physical examination, tests used to diagnose hypothermia include:
- Arterial blood gas determination
- Blood tests
- Hematocrit levels
- potassium levels
- blood glucose levels
- Coagulation tests
- Imaging tests
- Chest X-ray
- Computerized tomography (CT) scan of the head for trauma
- Electrocardiogram (ECG or EKG)
What Is the Treatment for Hypothermia?
Hypothermia is a medical emergency. If signs of hypothermia are present, take the person’s temperature. If it is below 95°F/35°C call 9-1-1 or get the person to a hospital’s emergency department right away.
If a person’s temperature is above 95°F/35°C or while waiting for first responders, attempt to warm the person. First aid for hypothermia includes:
- Moving to a warmer place as soon as possible
- Removing wet clothing
- Covering the person with blankets; use an electric blanket if possible, making sure the center of the body (chest, neck, head, and groin) is covered and not wet
- Provide warm beverages if the person is able to drink
- Avoid alcohol
- Do not try to give fluids to an unconscious person
If frostbite is suspected, do not massage or rub affected skin because it can cause damage.
Severe hypothermia is treated in a hospital and treatment may include:
- Blankets, heating pads, warm baths, or heaters that blow warm air to help bring a person's body temperature back up
- Warm fluids given intravenously (IV)
- Warm oxygen to breathe, or a breathing tube if needed
- Warming the inside of the body with water
- Medicines to treat related issues like low blood pressure or heart problems
- Blood rewarming
- A special machine draws blood out of the body, warms it up, and puts it back in
What Are Complications of Hypothermia?
Complications of hypothermia may include:
- Cardiac arrhythmias at temperatures below 86-89.6°F/30-32°C
- Aspiration pneumonia
- Pulmonary edema
- Bleeding diathesis
- Bladder atony
- Electrolyte abnormalities (high potassium, low blood sugar)
- Hematocrit, coagulation study abnormalities
How Do You Prevent Hypothermia?
Hypothermia can often be prevented by:
- Not staying outside in the cold for extended periods
- Dressing warmly and wearing layers
- Remove wet clothes as soon as possible once you get to a warm place
- Make sure children are dressed warmly and don’t let them play outside in the cold for long periods
- Make sure the homes of elderly people are sufficiently heated in winter
- Don’t drink too much alcohol
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