Bioethics News

Human cryopreservation. Technique and ethical and moral assessment

Cryopreservation consists of preserving human individuals or organs at very low temperatures (less than -130°) in order to preserve them. The low temperatures decrease the metabolism and facilitate preservation.

Technique

Cryopreservation begins by bringing the person to a state of hypothermia as quickly as possible in order to reduce cell damage. Anticoagulants (heparin) and vasodilators (nimodipine) must also be administered.

When cardiorespiratory arrest has occurred, the patient must be placed in a support or container that is suitable for inducing hypothermia (iced water or other alternative systems). Cardiopulmonary support manoeuvres are performed, treatments are administered and intravenous lines are inserted that allow the blood to be exchanged for cryoprotectant solutions.

At least one artery and one vein must then be cannulated in order to enable the exchange of blood for a cryoprotectant solution (usually ethylene glycol, dimethyl sulfoxide or other components) that prevents the formation of ice crystals, allowing vitrification of the cells while preventing damage due to the crystals. Exchanging the blood for a cryoprotectant solution takes place at hypothermia temperatures — preferably less than 10°C — since at these temperatures the solution can transport as much oxygen as blood. Once the blood has been exchanged for the cryoprotectant, rapid cooling below 0°C should be performed. This cooling can be carried out with dry ice, which allows the temperature to be lowered to -79°C, or with liquid nitrogen, which enables a temperature of -196°C to be reached. Nevertheless, once a temperature of -130°C has been reached, arrest of the cell’s biological time is complete and the procedure can continue slowly until it reaches the -196°C of liquid nitrogen.

The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.