Why are cold temperatures so dangerous if you have an accident? And why is it that cold temperatures enable some patients to survive without permanent harm?
Gemini has been quizzing doctor Sigurd Mydske and Øystein Wiggen, who is a research scientist at SINTEF and a cold temperature physiologist, all about what you need to know if you have an accident in the mountains during your Easter holidays, out on the road or in other cold situations.
As a physiologist, Wiggen conducts research into what the human body can tolerate under low-temperature stress. Mydske is a doctor and researcher at the Mountain Medicine Research Cluster at the Norwegian Air Ambulance Foundation (SNLA). The research cluster is a joint undertaking involving the Bergen Health Trust, the University of Bergen and the SNLA.
Together with their colleagues, Mydske and Wiggen are carrying out important work looking into finding the most optimal way of treating patients suffering from hypothermia.
Mountain medicine involves the prevention and treatment of medical issues that may arise in mountainous terrain. It is based on the premise that in the mountains, external conditions create challenges that can make even simple medical examinations and interventions very challenging.
Mountain medicine skills may be useful for a number of specialists, but are particularly applicable to physicians working outside hospitals such as municipal doctors, anaesthesiologists or those simply taking part in day trips or longer expeditions.
Medical conditions subject to research in this context may include hypothermia, frostbite, altitude sickness and physiological issues related to altitude, as well as topics such as expedition medicine, avalanches, anaesthesia and analgesia under primitive conditions, toxicology and traumatology.
In international terms, research and development topics linked to mountain medicine are brought together under two organisations in particular – the International Society for Mountain Medicine, ISMM (www.ismm.org) and the Medical Committee of the International Commission for Alpine Rescue (ICAR MedCom; www.alpine-rescue.org).
“Recent and robust knowledge in this field may have life-saving significance for patients who become involved in anything from avalanches to traffic accidents, as well as those who find themselves injured and unable to move on a cold cellar floor”, says Wiggen.
However, there is already a lot that doctors and researchers are certain about when it comes to applying know-how to save lives in cold environments.
How cold do we have to be before we can say it is dangerous?
“A person can be said to be hypothermic when his or her body temperature falls below 35°C”, says Øystein Wiggen. “To be precise, our core temperature is defined as that of the blood in our right cardiac ventricle. Hypothermia can develop into something very dangerous, but it usually takes some time before our core temperature becomes so low”, he says.
Why can it be so dangerous to get cold? After all, some people swear by a cold bath.
According to Sigurd Mydske, a large drop in body temperature can be dangerous for many reasons. Firstly, our blood platelets cease to function normally when our bodies become hypothermic. This makes it difficult to stop both external and internal bleeding. No wonder that sustaining an injury in cold conditions can be very serious. Secondly, low temperatures can be harmful in their own right. In the event of an accident, keeping the injured person warm is one of the most important things you can do.
- Click here to read about health researchers and their award-winning innovation for saving lives under cold conditions (in Norwegian)
“Even a drop in core temperature from 36 to 35 degrees may have serious consequences”, says Mydske. “Our body temperature helps to control the speed of all the chemical processes taking place in our bodies. When we become hypothermic, everything begins to slow down. Our vital organs such as the heart, lungs and brain function less efficiently, and the blood’s ability to coagulate is impaired. There is also a significant increase in the risk of cardiac arrest”, he says.
You can read about the health-giving effects of cold temperatures in the article;
So, what is really happening in a hypothermic body?
Researcher Øystein Wiggen explains:
“Firstly, the body has built-in mechanisms that work to prevent it from becoming seriously hypothermic. These include reducing blood supply to the peripheral parts of the body while increasing supply to the internal organs. The most important parts of the body are thus kept warm and continue to receive oxygen and nutrients. This also means that we feel the cold first in our noses, hands and feet. Secondly, the body starts to shiver. Shivering stimulates energy use and leads to increased heat production.
For example, if you’re caught in bad weather in the mountains and are becoming hypothermic, you may only need a couple of rubbish bags to save your life.
“Shivering in itself is not dangerous. It is in fact a sign that the body is doing its job”, says Mydske. “Danger arises when a person has become so cold that he or she stops shivering”, he says.
“Our temperature controls most of the processes that take place in our bodies”, says Mydske. “When we get very cold, our heartbeat and breathing slow down and become less stable. This also applies to the brain and our levels of consciousness. The brain gradually functions less effectively, and we become confused, lethargic, aggressive in part, and eventually unconscious. Our rate of metabolism, which uses oxygen to convert our food and drink into energy, declines. Our blood platelets become less viscid and stick together less well, which increases the risk of bleeding. This is why, after ensuring that a patient’s airways are clear and applying CPR, the most important thing is to keep her warm”, he says.
Facts: four ways of losing heat
The differences in temperature and humidity between the body and its surroundings are the factors that determine heat loss efficiency. The bigger the differences, the greater the heat loss. There are in fact four mechanisms that control heat loss.
- Evaporation, which is the process by which moisture leaves the body as a gas. This is why we should always change into dry clothes if we have been sweating or are soaked with rain after going out. Moist skin acts to cool the body because heat is carried away when the moisture evaporates.
- Conductive heat loss. This is where heat is lost from the body when, for example, we sit down to rest on a cold rock. Heat is transported from a warmer to a cooler place. This is why insulating camping mats are useful because they prevent heat being lost from our bodies into the ground.
- Convection, including wind chill. Convection is the mechanism by which we become cold due to the effect of wind or when we are travelling at high speed. It is the reason why it’s a good idea to carry a robust wind sack in your rucksack on long trips because this offers protection against both wind chill and evaporation.
- Radiation. There will always be heat loss by radiation from a warmer to a colder object. This is a basic law of physics. You will experience this if you stand in your shorts close to a cold wall in summer. It will be like feeling a cold gust of wind. In practice, we lose very little heat by radiation if we are fully clothed.
How long does it take to become dangerously cold?
“It’s impossible to say”, says Øystein Wiggen. “It depends on so many factors such as air temperature, wind conditions, your clothing, age and body shape. So, together with your first aid kit, it’s just as important to carry a good insulating mat, extra clothes and a bivouac bag in your pack”, he says.
“A good rule of thumb for a healthy person is that if you fall into cold water and manage to keep your head above the surface, you will have about 30 minutes before you become hypothermic (where your body temperature falls below 35° C)”, says Wiggen “This is why it is so important to be accompanied, and to carry a rope, ice safety picks and warm clothes when skiing or skating across a frozen river or lake. In the spring, when the snow and ice are starting to melt, it makes sense to bear these things in mind”, he says.
Some say that you shouldn’t try to warm up hypothermic patients. Others say the opposite. What is the right thing to do?
“The established idea that you shouldn’t try to warm up hypothermic patients goes back to the 1950s”, says Mydske. “This so-called knowledge is derived from old myths for which there is no scientific evidence. Unfortunately though, many people still believe this to be true”, he says.
According to Wiggen, contemporary advice is to adhere to the following drill:
- Insulate the patient from the cold by removing him or her from contact with any snow or ice. Use a rucksack or a mat as insulation. Everything helps.
- Place a moisture barrier as close against the patient as possible. In practice: Place the patient in a zipped-up wind sack to prevent losing moisture from the body. Evaporation cools the body down. This is why we sweat when we become too hot. Then get the patient into a sleeping bag or under a wind sack. The more insulation you can provide, the better.
- In all situations you must try to provide the patient with ‘active warming’. Active warming means providing warmth using devices such as heating mats. However, we still do not know exactly what effect this has. But, because it is normal for the body to be warm, we should always be looking to insulate the patient and provide active warmth.
“But be careful”, says Mydske. “A patient being warmed in this way must be closely monitored in order to prevent burns”, he says, going on to add;
“If you’re caught in bad weather in the mountains and are becoming hypothermic, you may only need a couple of rubbish bags to save your life. Jump into a bag, pull it over your head and make a hole to breathe through. Plastic bags can withstand harsh conditions much better than thin rescue blankets. They are windproof and cost next to nothing. Doing this will prevent heat loss due to evaporation and will have a big impact on your temperature”, he says.
“If we can keep the wind out, we can create a safe microclimate in the bag”, says Wiggen. “A lot will then have to happen before you freeze to death”, explains Wiggen. “A bivouac bag can save your life. Be aware that thin foil emergency blankets do not have the same effect. They are difficult to use both as a moisture barrier and as protection against the elements because they tend to become caught by the wind.
We doctors always say that a patient isn’t dead before he or she is both warm and dead.
“Foil blankets may be effective in reflecting radiated heat, but when we are clothed the amount of heat we lose by radiation is very small, so the effect is minimal”, says Wiggen. “This is why more and more rescue services are no longer using the foil blankets that we commonly see in the news coverage of disasters such as the recent earthquakes in Turkey and Syria. However, specially-designed bags are available that are well suited to this purpose. They are light, thin and moisture-proof, and reflect the heat radiated from the body. They are sold in sports retailers that offer a good selection of mountain equipment”, he says.
“But, remember”, says Mydske. “We doctors always say that a patient isn’t dead before he or she is both warm and dead. If a patient is becoming hypothermic, but the heart is still beating on its own, it is important to provide him or her with as much warmth as possible. If the patient’s heart has stopped beating, then you must start CPR. It is important not to give up before the patient has arrived at the hospital. In any event, it will not be possible to warm up such patients outside a hospital, so it is less important to make the effort to provide them with warmth.
Why is it that some people survive because of the cold?
“Paradoxically, it can happen that cold temperatures actually contribute towards a person surviving, for example in cases of falling into cold water”, says Wiggen. “When our bodies are cooled down, all our internal processes function more slowly. Our brains are able to tolerate long periods starved of oxygen before our condition becomes critical. However, in spite of the fact that the cold can save us in some situations, most incidences of prolonged submergence in cold water will result in unfortunate outcomes”, he says.
Is there anything we don’t know about the treatment of hypothermic patients?
“We can’t say for certain that we have identified the optimal treatment approach to so-called pre-hospital warming of hypothermic patients”, says Wiggen. “We are aware of the basic principles, but we need better equipment to facilitate active warming and, not least, methods for the easy and accurate measurement of body temperature out in the field. This is exactly what we are currently working on. In a few years’ time, we hope that it will be possible for mountain rescue personnel to reverse hypothermia even more effectively so that they can deliver warm patients to our hospitals”, he says.
In conclusion: Why do we sometimes feel warm immediately before we actually die of cold?
“Our brain controls the body’s physiological processes”, says Mydske. “It regulates the dilation of our arteries when we are hot, and their contraction when we are cold. But when this centre in our brains becomes cold, this mechanism stops working. In a seriously hypothermic body, the ‘sluices are opened’ and blood flows out into the hands and feet. Tense muscles are allowed to relax. The patient experiences this phenomenon as warmth, but in fact the body is losing heat. This, in combination with loss of brain function, explains why some people who have frozen to death have been found with their clothes removed”, he says.