Cryonics is a complicated process and it takes quite some time to complete the whole process before a person has been frozen.
When a person's heart stops beating, they are usually declared dead and before that doctors might try to resuscitate them by pumping their heart.
Cryonic doctors do not resuscitate the patient immediately but directly work on preserving the body instead in the cryonic lab.
The cryonic doctors take the patient to the lab and in the mean time they pump oxygen and blood into the brain so that the person does not become brain dead.
They stabilize the body to perform minimal function until they reach the facility.
It is here they start performing the freezing process.
The body cannot be frozen directly because the water in the cells also tends to freeze and since water expands after freezing, it may end up breaking the cells.
The water is replaced with a glycerol liquid, which does not freeze and is called a cryo-protectant.
Then the whole body is prepared through a process of vitrification which keeps the cells, tissues and organs from becoming ice and keeps it in a cool temperature.
After the vitrification process is over, the body is cooled on dry ice to reach a temperature of -130 degrees centigrade and then the body is immersed upside down in a container for preservation.
It is kept upside down because even if the tank leaks the brain is still immersed in the freezing liquid as a back up.