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Heart first aid

Not long ago, Gao Yixiang’s sudden death caused many people to pay attention to cardiac rescue. Cardiac arrest has a very high mortality rate. Even if he is lucky to survive, a few minutes of cerebral ischemia will cause irreversible brain damage. However, if the patient is induced to enter the artificial hibernation state in time, the occurrence of injuries can be slowed down and time can be gained for further treatment. Clinical practice has proven that this method can improve the survival rate of emergency patients and reduce the risk of nerve damage. In 2013, the famous racing driver Michael Schumacher applied this technology to the treatment of brain injuries.

Hibernation cryotherapy | Image source sinaiem

In hibernation cryotherapy, an ice pack or ice blanket is used to cool the patient’s body, or even a catheter is inserted into a blood vessel to cool the body by circulating the salt solution in it, which can generally be reduced to 32 ~ 34 ° C. During this period, the patient’s physical signs need to be monitored in real time to keep it stable. This process lasts about 12 to 24 hours, and then slowly returns to the patient at a rate of 0.25 to 0.5 ° C / h. Too fast temperature recovery will lead to complications such as hypotension and hypoglycemia due to vasodilation.

The technology of artificially induced hibernation can not only save lives, but also open up and continue the future of humankind. In many sci-fi movies, such as “Wandering Earth”, in order to enable astronauts to spend a long interplanetary voyage in a limited life, they will be put into a dormant state to extend their life, while also reducing material consumption and lightening the load on the spacecraft. . Currently, NASA (NASA) and European Space Agency (ESA ) are developing hibernation technologies suitable for space, for manned Mars exploration missions, and even future interstellar migration.

Simulation chart of artificial hibernation of space capsule

However, at present, humans cannot maintain artificial hibernation for a long time. After all, the human body still lacks the regulation mechanism of hibernating animals. If metabolic waste is not discharged for a long time, toxins will accumulate in the body and cause damage. Even with Mars at the doorstep of the earth, with existing technology, it still takes about six months to reach, not to mention exoplanet planets that require tens of thousands of years of journey to reach.

Frozen biological tissue

Wood Frog Hibernating | Photo Credit naturenorth

Are there any ways to achieve long-term sleep? Returning to the hibernating animals mentioned at the beginning, the wood frog that can hibernate for 7 months is the “sleeping god” in the hibernating animal world. But its dormant mode is not what ordinary animals can tolerate-freezing itself at sub-zero temperatures. This is a fatal danger for many animals. Ice crystals inside and outside the cell will damage the tissue structure, and the coagulated blood will not function normally.

The secret of wood frogs surviving even if their bodies are frozen is the cryoprotectant in their body, the high concentration of glucose in the blood. At the same time as the wood frog’s body started to freeze, its liver also worked overtime to break down glycogen into glucose. After reaching a certain concentration, even if the blood freezes, it will not form ice crystals, but will become syrup-like and will not hurt And cells.

There are many other animals, plants, and microorganisms that endure low temperatures through similar mechanisms. For example, “the strongest creature on earth”, water bear worms accumulate trehalose in the body when the ambient temperature decreases to prevent damage caused by water crystallization.

Water Bear Worm

Scientists from these hardy creaturesInspired by his body, he invented the vitrification technology (vitrification) , which solves a major problem of maintaining cell tissue structure and activity in the frozen state. Glass is an amorphous material. Some liquids, such as water, that would otherwise solidify into hard crystals will form an amorphous state similar to molten glass after vitrification. Vitrification of water can be achieved by rapid freezing at a high speed or by adding a cryoprotectant. The cryo-electron microscope technology, which won the 2017 Nobel Prize in Chemistry, uses vitrification to prevent water from crystallizing in biological tissues in order to maintain the original appearance of its internal structure.

Liquid nitrogen cryopreservation of cell tissues

The technology of cryopreservation of human cells and tissues is now quite mature, and it is not uncommon to successfully cultivate test-tube babies with frozen sperm or eggs. However, cryopreservation of larger organs is still quite difficult.

Controversial cryonics

Nevertheless, as early as the 1960s, people began to try to freeze the human body.

In 1966, the body of a Los Angeles woman was preserved in liquid nitrogen, but only two months later, it was thawed and buried.

In 1967, a few hours after James Bedford, a professor of psychology at the University of California, died of cancer, the body was frozen by Robert Nelson, president of the Cryonics Society of California, and others. Although Nelson was later prosecuted for unfreezing a group of remains, Bedford’s remains are still preserved to this day. This is also the first human body in history to be frozen for future resurrection.

In 1976, the cryonics institution was established, and the body of its founder Ettinger was frozen in 2011.

In the 1990s, cryobiologists Gregory Fay and Brian Walker invented a cryoprotectant to preserve transplanted organs, and tried to use it for cryopreservation of animal brains. Nothing was found after thawing. Damage caused by ice crystals, but the toxicity of cryoprotectants and dehydration of cells can still cause damage.

In 2015, Ms. Du Hong, a writer for children’s literature and one of the editors of Trisomy, died of pancreatic cancer, and her body was handed over to the Alco Life Extension Foundation (Alcor) Keep frozen.

In 2016, a cryobiological research company made progress in the study of cryopreservation of small animal brains. Under the electron microscope, the rabbit brain cell membranes, synapses, and intercellular structures preserved with stabilizers are very intact. However, some researchers have pointed out that the proteins in them have been chemically cross-linked, and they can not prove whether the neural pathways that store brain information are intact.

The technology used to freeze the human body is called the cryonics method (Cryonics) , which usually saves the entire human body at a low temperature of -196 ° C or Head, in the hope that future science and technology can revive it. There are many such subjects in science fiction works. For example, in “Three Body”, the three body person reshapes their body and consciousness through Yun Tianming’s brain.

Human Freezers

In fact, the scientific community has not yet accepted the cryonics method, and believes that this practice is contrary to the laws of natural sciences such as physics, chemistry, and biology. In many countries, the use of cryonics is banned, and if allowed, it is limited to remains that have been medically determined dead. At present, several companies providing cryogenic service technology are only distributed in the United States and Russia. Some companies have previously closed down and thawed the remains.

It can be understood that people with terminal illnesses treat cryonics as the last straw, but there are still many problems with this technology. For example, the high-concentration cryoprotectant used in the preservation of corpses, although it can preserve the integrity of tissues, it will poison cells. On the other hand, whether the human body can remain intact during thawing is also unknown. Even if thawing can proceed smoothly, reconstructing the human body is a huge project that requires nano-medical technology that goes deep into the molecular level. The most fundamental problem is the repair of brain memory and consciousness. No matter how well the neural structure is preserved, it is still a mystery whether memory and consciousness can be repaired only through the restoration of neural structure.