We are back with more on hypothermia. In this post, we will define this condition. We want to give you some basic information on hypothermia. In the next post, we will deal with reacting to hypothermia signs and symptoms. Keep warm, keep active and stay safe!
What is hypothermia?
Hypothermia is defined as having a core body temperature below 35°C (95°F). It occurs when the body loses excessive heat, is not able to generate enough heat and/or if there is a problem with the ability to control core temperature due to failure in thermoregulation.
How does your body regulate its temperature?
Your brain is very good at keeping your body within an optimal and very narrow range of temperatures, from 36.5°C to 37.5°C, through a feedback mechanism from the skin and central nervous system thermoreceptors. When the brain senses that your body is getting too cold, it will attempt to raise your core temperature by causing you to shiver, to generate heat and to constrict the vessels in your extremities to shunt warm blood toward your core, where the heart and other essential organs are located. This happens automatically. Your brain also prompts you to change your behavior by seeking shelter, putting on extra layers and increasing your physical activity to decrease heat loss and generate more heat, respectively.
How to recognize hypothermia
Once your core temperature drops below the optimal range, the body function starts to break down. Most of us don’t carry a thermometer when we are outdoors, so here are signs and symptoms of hypothermia you might encounter during the four stages of hypothermia:
I. Mild hypothermia: 32-35°C (90-95°F): shivering, awake, increased heart rate, poor judgement
II. Moderate hypothermia: 28-32°C (82-90°F): shivering (eventually stops), depressed mental status, might develop irregular heart beat, 25% decrease in oxygen consumption
III. Severe hypothermia: 20-28°C (68-82°F): no shivering, unconscious, low heart rate, decreased respiratory rate, prone to arrhythmia, 50-75% decrease in oxygen consumption
IV. Profound: <20°C (68°F): unobtainable vital signs, very prone to deadly arrhythmias
The lowest ever recorded temperature in an adult survivor of accidental hypothermia is 13.7°C. It’s a remarkable story of Anna Bagenholm, who got trapped under the ice in a ski accident. She was airlifted to a hospital in Tromso, Norway. After prolonged resuscitation, she was able to walk out of the hospital. (Hit the link for the BBC documentary of Anna’s story!)
The key here is to recognize hypothermia early. The assessment of mental status is the most important step. If you or one of your team members is starting to shiver, or more importantly, have a change in activity or interaction, that is a sign of getting too cold. Note that even in mild hypothermia, this individual might have poor judgment. They should not be left alone! (We will cover more on this next time.)
In more severe hypothermia, the patient might be unconscious and it might be hard to determine the exact cause without having a thermometer and getting additional history from bystanders. Many conditions mimic the signs of hypothermia, such as head injury, low blood sugar level, low oxygen level (from drowning or asphyxia with snow in an avalanche) and intoxication. Consider the most likely possibilities in your settings. In the field, it is often prudent to initiate a broad treatment plan while arranging for definitive care.
Stay tuned for our blog on hypothermia treatment!