Why Freeze Blood?
The Blood Connection preservation of rare blood types is important so that they will be available when needed for transfusion. Also, sometimes a surgery date is changed for the person who is giving autologous blood units. Freezing extends the dating period or shelf-life for these blood units.
How long can frozen blood be stored?
Frozen blood can be stored for 10 years from the date of blood collection.
How is blood kept “alive” during the freezing process?
A special cryoprotectant chemical is added to the blood cells. This chemical, glycerol, permeates the red blood cell membrane so that there is about as much glycerol inside the cell as outside the cell, and it displaces much of the cell’s water. This balances the pressures inside and outside the cell. When the cells are frozen, the glycerol freezes very uniformly without much formation of water ice crystals that could swell and burst the cell. In addition, the cells are frozen at very low temperatures (minus 122.80F or lower). This places the cells in a state of suspended animation.
What does a frozen bag of blood look like?
A frozen bag of blood looks like a solid, thin, flat, rectangular plastic-encased cake of red ice. That is because the blood cells and the glycerol are first placed in a sturdy, specially formulated plastic bag. The bag is then placed in a flat metal container about the size of a clipboard portfolio. Thus, the bag inside the metal canister is squashed flat. This means the blood cells are spread over a large surface area, and this helps speed up the freezing of the bag when the metal canister and enclosed bag are placed in the freezer.
How is the frozen blood prepared for transfusion?
It is thawed and the glycerol removed. The frozen bag is placed in a water bath that is set to body temperature (98.6F). The thin, flat bag thaws within a few minutes. Because rapid glycerol removal damages the red cells, the glycerol is removed in stages through a series of washings with progressively more diluted salt solutions. Finally, the red cells are suspended in a solution that consists of salts needed for water pressure balance, sugars needed for cell energy, and preservatives to enhance cell survival over time. The cells at this point are once again vitally active in metabolism and are ready to be transfused to a patient.