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Hypothermia and Its Applications in the Medical Field

Discover the impact of cold temperatures on the healthcare system.

The use of cold temperatures in the medical field is not a new thing. Hippocrates, circa 450 BC , recommended packing snow into those who were wounded in battle. He noticed that they had a higher survival rate when the body heat was low (but probably didn’t completely understand why). Over the years, scientists and researchers have studied the effects of the cold on the body extensively. From frostbite to therapeutic hypothermia, great strides have been made. We understood how to embrace this natural element and use its effects to our advantage. Now, lives are saved every day thanks to clinical temperature regulation. In some cases, lowering it by a few degrees is enough. In others, we must drop it several hundred degrees below zero. In this article, we will look at hypothermia and its relative, cryogenics. How is cold helping us in emergency medical situations? And what is cryonics?

Hypothermia: The Effects of a Few Degrees Less

Hypothermia is a condition that, if it occurs without medical supervision, can damage an organism. In extreme cases it can lead to death as organs do not function normally when the body heat is lowered.

Now, you might ask yourself at what temperature a person’s body enters a state of hypothermia? Core body temperature is incredibly stable. Normally, it is around 37°C. When it rises to 38.5°C or more, you have a fever. When it drops a couple of degrees (below 35°C) - hypothermia occurs. 

Let's see what happens in detail. When exposed to cool climates, the body loses heat mainly through the skin (about 90%). The rest escapes from the lungs during exhalation. If the body is immersed in cold water, its temperature decreases 25 times faster. Of course, if the temperature drops only slightly, there’s no serious damage. The body starts shivering to increase core heat and our survival instinct kicks in, leading us to find a source of warmth. In some cases, a brief chill discomfort can even have beneficial effects on the body. But if the degrees continues to drop and no quick remedy is found, the body slowly starts to crash. 

In an attempt to preserve heat, blood vessels temporarily narrow due to an effect called vasoconstriction. Normally, the heart and liver are the organs that produce the most warmth. However, when the temperature decreases, they reduce their activity, even to the point of shutting down completely in extreme cases. In this way, they try to conserve energy and protect the brain. The moment there’s a cardiac arrest, the process of death begins.

Targeted Temperature Management in Medicine

It might seem counterintuitive that doctors purposely induce hypothermic states. Yet, when done in a controlled way and in the right moment, this technique can save lives.

Let me introduce to you targeted temperature management (TTM), a system currently used to induce hypothermia and, in some cases, prevent fever, or maintain normothermia. American neurologist Temple Fay published one of the first scientific papers related to this technique back in 1943. By testing systemic and focal cooling, Fay observed improved outcomes after traumatic brain injury (TBI) when temperatures were lowered from 38.3°C to 32.7°C. However, it’s only in 2002 that therapeutic hypothermia began getting serious attention after two controlled trials published in the New England Journal of Medicine showed significant benefits of lowering core temperatures in patients with cardiac arrest [1][2].

Today, targeted temperature management is a standard protocol to handle post-cardiac arrest patients. It aims to reduce mortality, and improve neurological outcomes in unresponsive patients who achieve return of spontaneous circulation (ROSC) after cardiac arrest. Once circulation is restored, cooling is achieved by two main methods: surface and endovascular cooling

Surface cooling includes convective air blankets, water mattresses, alcohol bathing, cooling jackets, and ice packing. Endovascular cooling is done by infusion of cold isotonic fluid and has the benefit of reaching target temperatures faster. The goal is to achieve a core temperature of 32°C to 34°C as soon as possible, maintain this temperature for 12 to 24 hours, and then rewarm at a controlled rate of 0.2 to 0.5 °C/hour[3]. 

What Are the Benefits of Inducing Hypothermia?

Hypothermia acts on three main temperature-dependent pathological processes: ischemic brain injury, reperfusion injury, and secondary brain damage. Let’s look at the first one. 

Ischemia is defined as inadequate supply of oxygenated blood to one or more parts of the body. When the heartbeat ceases, blood stops circulating. This causes cells to run out of oxygen and turn from aerobic to anaerobic metabolism. They produce lactate and other waste products to the point where they start to self-recycle and die. This can lead to serious brain damage.

Induced hypothermia can have a deeply positive impact on reducing ischemia due to its metabolic slowing effect. When the temperature is lowered by 1°C, metabolic activity drops by 5% to 7%. This translates into a significantly lower need for oxygen. If the cells require lower levels of oxygen, there’s more time to resucitate the patient while causing less brain damage.

Additionally, temperature regulation prevents the onset of pyrexia aka fever. This is a fairly common effect of post-cardiac arrest syndrome. Beside being detrimental for an already impaired body, fever is linked to adverse outcomes in all types of neurologic injury.

plastic brain
The warmer the temperature, the more ischaemic damage can be

Cryogenics: From Mild Cold to Very Cold

Now, with hypothermia there’s a decrease in body temperature of a few degrees. But what happens if this is lowered by tens or even hundreds of degrees? This is what cryogenics, the science that studies the behavior of substances at very low (or cryogenic) temperatures, is all about. We are talking a range from −150°C to absolute zero (−273°C)! The ultra-low temperatures change the chemical attributes which open a gateway for a variety of new applications. 

There are two main medical applications: cryotherapy and cryopreservation. 

  • Cryotherapy was used in the past to heal wounds and relieve pain. Today, it’s used to treat a variety of skin conditions (including warts and skin tags) and some cancers, including prostate, cervical and liver cancer. 
  • Cryopreservation is the process of preserving cells, tissues, semen, embryos, organs and human beings with extremely low temperatures. This reduces metabolic rate to a point where biological activity is completely paused. Cryopreserved organic materials are usually stored in liquid nitrogen and can remain in this state indefinitely. The idea behind this technology is to preserve organic material that can later be rewarmed and utilized (or revived in the case of human cryopreservation).

In recent years, a trend has developed that also goes by the name of whole-body cryotherapy. The person receiving this treatment usually sits in a cryogenic booth for 3-5 minutes, having their bodies exposed to extremely low temperatures. This type of cryotherapy can help with muscle pain, as well as some joint and muscle disorders, such as arthritis. It can also support the process of weight loss, reduce inflammation, prevent dementia and much more. Being a relatively new technique, the benefits require more scientific research.

Human Cryopreservation to Save Lives

TTM is a technique used in emergency medicine. Cryonics, or human cryopreservation, is also in its own way a procedure used in critical situations.

In ideal cases, immediately after a cryonics member's legal death, a standby team induces a state of controlled hypothermia. The temperature is lowered, and metabolic activity reduced. This way, the ischemia in the patient is reduced. 

Now, with this technique you don't just go down a couple of degrees but down to -196°C. An important factor comes into play: when you drop below zero, the water in your body freezes. To prevent the formation of ice, the blood must be replaced with cryoprotective agents (CPAs) and the water in the body is removed. As the temperature gradually decreases, the body enters a glass-like amorphous state. The patient is vitrified, and can remain in this state for an indefinite period of time.

When, in 50, 100 or perhaps 500 years' time, medical technology has developed sufficiently to cure the causes that led to the person's death, they can potentially be revived. Thanks to human cryopreservation, people who would be doomed today might have a chance to be saved in the future.


In the past, present, and future, cool temperatures used in a controlled manner have saved lives. While induced hypothermia gives medical professionals several minutes more to prevent brain damage, human cryopreservation might give them decades or centuries.

Obviously, research is necessary in order to make full use of the possibilities offered by these technologies. When it comes to human cryopreservation, it will take some time before revival might be possible. Nevertheless, many people think it’s a road worth trying. And you, what do you think? Let us know on our Discord server.

And in the meantime, if you feel like learning more about cryonics, take a look at our editorial Tomorrow Insight. I bet you’ll find answers to your questions.

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