Time Standing Still: How Cryogenics Might Make Eternal Life Possible

A photo showing different sizes of liquid nitrogen storage dewars.

For millennia, humans have attempted to find the key to eternal life. Going on quests for elixirs, reciting spells, and even drinking gold were just some of the efforts humans have made to keep death from their door. Humans today aren’t much different from their historical counterparts, still harboring a curiosity about immortality. The advancement of technology has made this fantasy seem more attainable, particularly with the development of biological preservation through cryogenics, a field that encompasses cryopreservation, cryonics, and suspended animation.

Cryopreservation

Cryopreservation is a process that preserves biological structures like cells and tissues by cooling them to temperatures well below freezing, usually -321°F (196°C). This procedure is most commonly used to freeze eggs and embryos for future use, but its purpose is bountiful, assisting with the storage of stem cells, blood, bone marrow, and genetic samples from both plants and animals. 

The controlled rate freezer (CRF) is largely considered the gold standard for cryopreservation because it can slowly lower the internal temperature of a sample, minimizing the formation of ice crystals, which can damage organelles, within it. In order to begin the cooling process, the freezer must be connected to a cryogenic storage dewar, though with more modern tools, this is not a requirement.

The storage dewar is a double-walled, vacuum-insulated container filled with liquid nitrogen, the key component in most forms of cryopreservation. Vacuum-insulated transfer lines move the liquid nitrogen to the CRF’s cooling chambers by either using pressure from the dewar’s vapor or external dry, inert gas. Once the liquid nitrogen and its cold vapor are transferred, the freezer uses sensors and fans to distribute it around the samples, suspending all biological activity.

While cryopreservation is best known for being used to freeze small biological structures, there have been attempts to use it for entire human bodies in a process referred to as cryonics. 

Cryonics

Cryonics is the practice of freezing legally dead human bodies, with the hope that future technology will be able to resurrect them. Since cryonics is based on cryopreservation, the procedures are essentially the same. Immediately after a person is declared dead, a team flushes out the body’s blood and replaces it with a vitrification solution. Then, a positive displacement pump circulates viscous cryoprotectants throughout the body, which replace intracellular water, preventing ice crystallization. The vitrification process transforms cells into a glass-like state, and it’s different from the gradual freezing method we see in CRFs, which only controls, not stops, ice crystallization.

The “patients” who undergo this process are stored just like the samples in ordinary cryopreservation, being placed in large cryogenic storage containers and kept in liquid nitrogen at -321°F (-196°C). Maintaining a stable temperature over decades requires specialized container design and passive cooling systems engineered to minimize heat transfer and mechanical stress. Both dewars and cryostats are used for cryogenic storage, but the Cryonics Institute claims that its cryostat design has more advantages than traditional cryogenic dewars. 

These custom-built fiberglass-resin cryostats are referred to as HSSVs (Hard-Shell, Soft Vacuum), which maintain low, but not extremely low, pressure, suppressing convection. They have an insulation system made of perlite, a volcanic glass with extremely low thermal conductivity, thus suppressing conduction. The thickness of their walls, with reports citing as much as thirteen inches, increases the distance heat must travel, lowering the overall heat flux. The cryostat’s design results in a greater tolerance to structural damage, but even if the vacuum insulation is partially compromised, the perlite will continue to allow temperatures to remain stable.

Patients have been stored in cryogenic units for decades, but there have been no successful revivals. Currently, cryonic facilities focus solely on maintaining stable long-term storage through the continuous monitoring of liquid nitrogen levels and vacuum integrity. While the technology prevents tissue structures from deteriorating, there have been no reliable developments to restore biological function. All potential revival methods remain hypothetical.

Suspended Animation

A diagram showing where Emergency Preservation and Resuscitation (EPR) comes into play following a trauma-induced cardiac arrest.

Although cryonics seeks to preserve the body after death, a concept called suspended animation applies similar principles to living humans. It is defined as the temporary slowing of biological processes, achieved by lowering the body’s temperature to around 50-59°F (10-15°C). The most advanced example of this is Emergency Preservation and Resuscitation (EPR), a procedure used on patients who lose their pulse after a cardiac arrest induced by traumatic injury. EPR begins with an intra-aortic perfusion of cold saline solution. The goal is to reduce metabolic activity, granting surgeons time to operate on the patient.

The core of the EPR system is the aortic balloon catheter, which allows the saline solution to directly enter the aorta and also block distal blood flow. A perfusion pump controls the flow and pressure of the saline solution, while temperature sensors monitor, in real time, the rate and extent of the cooling of the body. Once the patient undergoes surgery and is found to be stable, they are gradually rewarmed using a cardiopulmonary bypass system (CBP). After the blood has been drained, oxygenated, filtered, and brought up to temperature in the CBP machine, it is pumped back into the patient’s circulatory system through an arterial cannula.

Suspended animation has only been proven to work for temporary purposes, with its long-term applications posing significant risks. Hypothermia can impair clotting and result in inflammation during the reperfusion process, leading to potential bleeding complications and even organ failure. Even though many individuals look towards suspended animation to stop cellular aging, that vision remains in the realm of science fiction for now.

True immortality has not been discovered yet, but modern technological developments have pushed the boundaries of eternal life. From preserving organs to temporarily slowing metabolism, human fascination with halting death is driving medical breakthroughs that have, and will continue to, save countless lives, even if it’s not forever.